allow add/update of a unison file with failing watches #9794

Job	Run time
ormolu	6s
build ucm (ubuntu-20.04)	2m 42s
build ucm (macOS-13)	11m 49s
build ucm (windows-2019)	5m 55s
generate jit source	11s
run transcripts (ubuntu-20.04)	4m 1s
run interpreter tests (ubuntu-20.04)	1m 5s
run transcripts (macos-13)	8m 2s
run interpreter tests (macos-13)	2m 4s
run transcripts (windows-2019)	7m 26s
build jit binary / build jit binary (ubuntu-20.04)	16s
build jit binary / build jit binary (macOS-13)	19s
build jit binary / build jit binary (windows-2019)	17s
test jit / test jit (ubuntu-20.04)	6s
test jit / test jit (macOS-13)	15s
	44m 34s

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