gh-119698: fix a special case in `symtable.Class.get_methods` #119962

Job	Run time
Check for source changes	11s
Check if generated files are up to date	5m 2s
Docs	0s
Address sanitizer	7m 24s
Ubuntu SSL tests with OpenSSL (1.1.1w)	2m 12s
Hypothesis tests on Ubuntu	5m 20s
Ubuntu SSL tests with OpenSSL (3.0.13)	2m 15s
Ubuntu SSL tests with OpenSSL (3.1.5)	2m 57s
CIFuzz	0s
Ubuntu SSL tests with OpenSSL (3.2.1)	2m 5s
macOS / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	4m 52s
macOS / build and test (macos-13)	8m 33s
macOS (free-threading) / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	5m 22s
Thread sanitizer / Thread sanitizer	4m 20s
Ubuntu / build and test	7m 44s
Thread sanitizer (free-threading) / Thread sanitizer	5m 43s
Ubuntu (free-threading) / build and test	9m 11s
WASI / build and test	6m 10s
Windows / build (arm64)	2m 54s
Windows (free-threading) / build (arm64)	2m 53s
Windows / build and test (Win32)	14m 58s
Windows (free-threading) / build and test (Win32)	23m 8s
Windows / build and test (x64)	15m 42s
Windows (free-threading) / build and test (x64)	22m 11s
All required checks pass	4s
	2h 41m 11s

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