fix(server): return METHOD_NOT_FOUND for unregistered spec methods (#3193) #3757

Job	Run time
checks / pre-commit	47s
checks / readme-snippets	15s
checks / docs	51s
checks / test (3.10, locked, windows-latest)	2m 7s
checks / test (3.10, lowest-direct, windows-latest)	2m 10s
checks / test (3.10, locked, ubuntu-latest)	1m 16s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 7s
checks / test (3.11, locked, windows-latest)	1m 58s
checks / test (3.12, locked, windows-latest)	2m 1s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 15s
checks / test (3.12, lowest-direct, windows-latest)	1m 54s
checks / test (3.11, locked, ubuntu-latest)	1m 14s
checks / test (3.14, lowest-direct, windows-latest)	1m 45s
checks / test (3.12, locked, ubuntu-latest)	1m 36s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 9s
checks / test (3.14, locked, windows-latest)	2m 15s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.11, lowest-direct, windows-latest)	1m 49s
checks / test (3.13, locked, windows-latest)	1m 56s
checks / test (3.13, lowest-direct, windows-latest)	2m 6s
checks / test (3.14, locked, ubuntu-latest)	1m 14s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 16s
checks / test (3.13, locked, ubuntu-latest)	1m 10s
all-green	3s
	34m 34s

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