Add signature for `Tap#config`. #25990

Job	Run time
syntax	47s
tap syntax	6m 0s
cask audit	2m 44s
vendored gems	47s
formula audit	6m 35s
docker	4m 58s
test default formula (Ubuntu 22.04)	8m 4s
update-test (Ubuntu 22.04)	1m 10s
test default formula (Ubuntu 20.04)	11m 5s
tests (online)	9m 36s
update-test (macOS 13)	1m 1s
tests (generic OS)	6m 38s
test default formula (macOS 13 x86_64)	8m 9s
tests (Ubuntu 22.04)	5m 54s
test default formula (macOS 14 arm64)	3m 52s
tests (Ubuntu 20.04)	8m 9s
tests (macOS 13 x86_64)	7m 44s
tests (macOS 14 arm64)	15m 0s
	1h 48m 13s

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