ci: give the test job 50 minutes so Windows can finish (#278)

Windows test runs today took 25-32 minutes when green, and slower runners
cut off three #270 runs and a release/v5-prerelease run at the 35-minute
limit with every test still passing. The build step alone ran 4-5 minutes
longer than usual, which left no headroom.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: mikolalysenko

.github/workflows/ci.yml

@@ -238,7 +238,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
-    timeout-minutes: 35
+    timeout-minutes: 50
     steps:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2