[3.14] gh-135368: Fix mocks on dataclass specs with instance=True (GH-135421)#135503

sobolevn merged 1 commit intopython:3.14python/cpython:3.14from

miss-islington:backport-c8319a3-3.14miss-islington/cpython:backport-c8319a3-3.14Copy head branch name to clipboard