Remove fish command completions for excluded commands #31302

Job	Run time
syntax	36s
cask audit	2m 25s
formula audit	4m 17s
tap syntax	6m 3s
test default formula (Ubuntu 22.04)	1m 23s
update-test (Ubuntu)	25s
tests (online)	5m 21s
vendored gems	39s
test default formula (Ubuntu 20.04)	2m 52s
update-test (macOS)	32s
tests (generic OS)	2m 44s
test default formula (macOS 13 x86_64)	3m 32s
test default formula (macOS 15 arm64)	1m 24s
tests (Ubuntu 24.04)	3m 6s
tests (Ubuntu 22.04)	3m 4s
tests (Ubuntu 20.04)	3m 40s
tests (macOS 13 x86_64)	7m 23s
tests (macOS 15 arm64)	5m 35s
	55m 1s

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