doc: drop 'breaking change' mark from 2.11.2 notes

The release notes states one change as breaking, but the new behavior
was enabled on 3.0 branch, see commit 6cb39116 ("box: set default
c_func_iproto_multireturn to new"), and not enabled on 2.11 branch.

Thanks @mons for the notice!

NO_DOC=no code changes
NO_CHANGELOG=see NO_DOC
NO_TEST=see NO_DOC

changelogs/2.11.2.md

@@ -146,9 +146,9 @@ were fixed as part of this activity:
   lengthy args, such as list of audit events (ghe-523).
 * Fixed crashes if `box.info.memory()`, `box.info.gc()`, `box.info.vinyl()`,
   and `box.info.sql()` are called before `box.cfg{}` (gh-9173).
-* **[Breaking change]** Added a `c_func_iproto_multireturn` option to the
-  `compat` module. The new behavior drops an additional array that wraps
-  multiple results returned via iproto (gh-4799).
+* Added a `c_func_iproto_multireturn` option to the `compat` module. The new
+  behavior drops an additional array that wraps multiple results returned via
+  iproto (gh-4799).
 * Fixed a bug that allows downgrading from a schema version more recent than
   a Tarantool version (gh-9182).
 * Fixed a bug when `on_shutdown` triggers weren't run if `os.exit()` was