feat: remove GraalPy 3.11 (gp311) support (#2895)

Drops the GraalPy 3.11 / GraalPy 24.2 builds (gp311_242) as agreed in
pypa/cibuildwheel#2741: a ~6-month overlap after the GraalPy 25 (gp312)
release. GraalPy 3.12 (gp312_250) stays.

This also removes the GraalPy 24-only workarounds that were explicitly
marked "Remove when GraalPy 24.x is dropped":
- the Visual Studio compiler-discovery (vswhere) and build-isolation
  (graalpython#491) workarounds in the Windows backend
- the issue-491 Windows skip/filter hacks in test_pep518 and
  test_dependency_versions (added in the original GraalPy PR #1538 and
  unneeded since GraalPy 25 per #2597)

The uv-doesn't-support-graalpy skip (#2754), the `graalpy` enable group,
and the generated constraints pins apply to all GraalPy and are kept.

Assisted-by: ClaudeCode:claude-opus-4.8

test/utils.py

@@ -319,7 +319,6 @@ def _expected_wheels(
 
         if EnableGroup.GraalPy in enable_groups and include_graalpy_in_expected_wheels:
             python_abi_tags += [
-                "graalpy311-graalpy242_311_native",
                 "graalpy312-graalpy250_312_native",
             ]
 
@@ -376,10 +375,7 @@ def _expected_wheels(
                 else:
                     min_macosx = _floor_macosx(macosx_deployment_target, "10.15")
             elif python_abi_tag.startswith("graalpy"):
-                if python_abi_tag.startswith("graalpy311"):
-                    min_macosx = macosx_deployment_target
-                else:
-                    min_macosx = _floor_macosx(macosx_deployment_target, "10.13")
+                min_macosx = _floor_macosx(macosx_deployment_target, "10.13")
             else:
                 min_macosx = macosx_deployment_target