gh-144702: Use standard terminology in class pattern error message (#… #2249

Job	Run time
aarch64-apple-darwin/clang	8m 8s
x86_64-pc-windows-msvc/msvc-free-threading	4m 42s
x86_64-apple-darwin/clang	18m 25s
aarch64-unknown-linux-gnu/gcc	7m 10s
x86_64-pc-windows-msvc/msvc	10m 15s
x86_64-unknown-linux-gnu/gcc-free-threading	9m 11s
x86_64-unknown-linux-gnu/gcc	9m 44s
	1h 7m 35s

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