Fix a bug in ReFitLevel() where `FileMetaData::being_compacted` is not cleared #2757

Job	Run time
build-linux-cmake-mingw	12m 12s
check-format-and-targets	23s
build-linux	16m 33s
build-linux-cmake-with-benchmark	19m 8s
build-linux-cmake-with-folly	27m 14s
build-examples	10m 45s
build-linux-cmake-with-folly-coroutines	31m 23s
build-linux-cmake-with-folly-lite-no-test	8m 1s
build-linux-encrypted_env-no_compression	15m 46s
build-linux-make-with-folly	27m 57s
build-linux-make-with-folly-lite-no-test	9m 18s
build-linux-release	14m 10s
build-linux-release-rtti	12m 9s
build-fuzzers	8m 55s
build-linux-clang10-asan	17m 1s
build-linux-clang10-clang-analyze	17m 2s
build-linux-clang10-mini-tsan	24m 4s
build-linux-clang-13-no_test_run	7m 13s
build-linux-clang10-ubsan	16m 15s
build-linux-clang-no_test_run	11m 47s
build-linux-gcc-10-cxx20-no_test_run	9m 20s
build-linux-gcc-11-no_test_run	10m 18s
build-linux-gcc-8-no_test_run	8m 41s
build-linux-java	14m 50s
build-linux-java-static	11m 37s
build-linux-mini-crashtest	29m 54s
build-linux-static_lib-alt_namespace-status_checked	18m 48s
build-linux-unity-and-headers	12m 53s
build-macos	20m 22s
build-macos-cmake (true)	51m 26s
build-macos-java	20m 45s
build-macos-cmake (false)	1h 0m 22s
build-windows-vs2019	52m 13s
build-linux-arm	14m 2s
build-linux-java-pmd	12m 2s
build-macos-java-static	26m 19s
build-macos-java-static-universal	26m 34s
	11h 47m 42s

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