Cleanup changelog/unreleased

changelogs/unreleased/add-fiber_set_ctx.md

changelogs/unreleased/downgrade.md

changelogs/unreleased/fix-bootstrap-with-er-readonly.md

changelogs/unreleased/fix-libunwind-h-search.md

changelogs/unreleased/fix-string-dequoting.md

.../unreleased/gh-2867-raise-on-raw-modifications-box.cfg.md

...logs/unreleased/gh-3012-yaml-prettier-multiline-output.md

changelogs/unreleased/gh-3159-recovery-triggers.md

changelogs/unreleased/gh-3211-per-module-log_level.md

changelogs/unreleased/gh-3682-uri-encode-decode.md

changelogs/unreleased/gh-4573-implement-fiber-top-for-arm.md

changelogs/unreleased/gh-4726-execute-field-in-box.md

changelogs/unreleased/gh-5064-ignore-i-flag-without-tty.md

changelogs/unreleased/gh-5272-bootstrap-strategy-auto.md

changelogs/unreleased/gh-5272-sync-timeout-default.md

changelogs/unreleased/gh-5522-vy-tx-isolation-level.md

changelogs/unreleased/gh-5541-proxy-luajit-flags.md

changelogs/unreleased/gh-5665-get-rid-of-fiber_gc.md

changelogs/unreleased/gh-5869-remove-fiber-top-cpu_misses.md

changelogs/unreleased/gh-6011-follow-env-vars-on-log-cfg.md