ci: scope pre-3.11 x86 exclude to windows-latest only

Partial revert of 5ec3877. The maturin/cryptography sdist-build issue
is Windows-specific (no cp38/cp39/cp310 win32 wheel and an x86_64-only
host Rust toolchain). On Linux and macOS x86 — if those cells are ever
re-enabled — the package would either use a Linux/macOS wheel or a
sdist build that doesn't have this architecture-mismatch failure mode.

Re-add `os: windows-latest` to each of the three pre-3.11 x86 excludes
so the rule expresses what it actually means. Effective coverage today
is unchanged (non-Windows x86 is still excluded by the existing
(os, architecture) rules above), but the intent is now correct if those
blanket excludes are ever lifted.

Author: josecorella

.github/workflows/ci_tests.yaml

@@ -73,13 +73,16 @@ jobs:
           # (Rust/PyO3). That build fails on the hosted windows-latest
           # runner because only the x86_64 Rust target is installed while
           # the interpreter reports platform `win32` (i686), so maturin
-          # refuses to use it. Until a host-side toolchain workaround
-          # exists, omit pre-3.11 Python from x86 testing entirely.
-          - python: 3.8
+          # refuses to use it. Drop pre-3.11 x86 on Windows only; non-
+          # Windows x86 (if ever enabled) is unaffected by this issue.
+          - os: windows-latest
+            python: 3.8
             architecture: x86
-          - python: 3.9
+          - os: windows-latest
+            python: 3.9
             architecture: x86
-          - python: "3.10"
+          - os: windows-latest
+            python: "3.10"
             architecture: x86
 
           # MPL is not supported on <3.11