doc: proofread 2.10.3 changelogs

Fix wording, punctuation, and formatting.

NO_CHANGELOG=changelog
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changelogs/unreleased/add-redos-7.3-ci-cd.md

 ## feature/build
 
-* Support RedOS 7.3 build.
+* RedOS 7.3 is now supported.

changelogs/unreleased/gh-4450-logger-sigsegv-revert.md

 ## bugfix/core
 
-* Fixed degradation introduced in Tarantool 2.10.2 that could cause log
-  messages to be written to data files thus causing data corruption.
+* Fixed a bug introduced in Tarantool 2.10.2: log messages
+  could be written to data files thus causing data corruption.
   The issue was fixed by reverting the fix for gh-4450.

changelogs/unreleased/gh-7086-box_issue_promote_demote_asserts.md

 ## bugfix/synchro
 
-* Fixed asserts in debug build/undefined behaviour in release when simulteneous
-  elections started/another instance promoted while instance was acquiring
-  or releasing synchro queue (gh-7086).
+* Fixed assertions in debug builds and undefined behaviour in release builds
+  when simultaneous elections started or another instance was promoted while
+  an instance was acquiring or releasing the synchro queue (gh-7086).

changelogs/unreleased/gh-7253-split-brain-early-vote.md

 ## bugfix/raft
 
-* Fixed a bug when a replicaset could be split in parts if a node during
-  elections voted for another instance while having some local WAL writes not
-  finished (gh-7253).
+* Fixed a bug when a replicaset could be split into parts if a node voted
+  for another instance while having local WAL writes unfinished (gh-7253).

changelogs/unreleased/gh-7343-unserializable-read-tracked-incorrectly-after-rollback.md

 ## bugfix/memtx
 
-* Fixed unserializable reads tracked incorrectly after transaction rollback
+* Fixed unserializable reads tracked incorrectly after transaction rollbacks
   (gh-7343).

changelogs/unreleased/gh-7434-yield-in-on_shutdown-trigger.md

 ## bugfix/box
 
-* Fixed a bug when `fiber.yield()` may break the execution of a shutdown
+* Fixed a bug when `fiber.yield()` might break the execution of a shutdown
   trigger (gh-7434).

changelogs/unreleased/gh-7449-tuple-is-dirty-assertion-on-replace.md

 ## bugfix/memtx
 
-* Fixed 'use after free' in transaction manager which could occur in certain
-  states (gh-7449).
+* Fixed `use after free` that could occur in the transaction manager
+  in certain states (gh-7449).

changelogs/unreleased/gh-7670-memtx-tx-manager-idx-rand-inconsistency.md

 ## bugfix/memtx
 
-* Fixed inconsistency of `index:random` in context of transaction management
+* Fixed an inconsistency in `index:random` in the context of transaction management
   (gh-7670).

changelogs/unreleased/gh-7685-memtx-tree-idx-get-with-nullable-field-phantom-read.md

 ## bugfix/memtx
 
-* Fixed possibility of phantom reads with `get` on TREE index containing
-  nullable part (gh-7685).
+* Fixed possible phantom reads with `get` on TREE indexes containing
+  nullable parts (gh-7685).

changelogs/unreleased/gh-7705-json-update-crash.md

 ## bugfix/core
 
-* Fixed a bug that a single JSON update couldn't insert and update a map/array
-  field in 2 sequential ops. It would either crash or return an error (gh-7705).
+* Fixed a bug when a single JSON update couldn't insert and update a field of a map or
+  an array in two sequential calls. It would either crash or return an error (gh-7705).

changelogs/unreleased/merger-use-after-free-in-gen.md

 ## bugfix/lua/merger
 
-* Fixed use-after-free during iteration over `merge_source:pairs()` or
+* Fixed `use after free` that could occur during iteration over `merge_source:pairs()` or
   `merger:pairs()` (gh-7657).

changelogs/unreleased/popen-mac-os-race.md

 ## bugfix/lua/popen
 
-* Handle a race in `<popen handle>:signal()` on Mac OS 12 and newer (gh-7658).
+* Fixed a race condition in `<popen handle>:signal()` on Mac OS 12 and newer (gh-7658).

changelogs/unreleased/promote-hang.md

 ## bugfix/raft
 
 * Fixed a bug when a node with `election_mode='voter'` could hang in
-  `box.ctl.promote()` or even become a leader.
+  `box.ctl.promote()` or become a leader.

changelogs/unreleased/strerror-mt-safe.md

 ## bugfix/core
 
-* Switched from MT-Unsafe `strerror()` to MT-Safe `strerror_r()`. Usage of the
-  unsafe function could result in corrupted error messages.
+* Switched from MT-Unsafe `strerror()` to MT-Safe `strerror_r()`. The usage
+  of the unsafe function could result in corrupted error messages.