fix: skip run-on-arch pytest for x86_64 in musllinux job

Author: Copilot

.github/workflows/CI.yml

@@ -110,7 +110,7 @@ jobs:
           name: wheels-musllinux-${{ matrix.platform.target }}
           path: dist
       - name: pytest
-        if: ${{ matrix.platform.target != 'x86' }}
+        if: ${{ !startsWith(matrix.platform.target, 'x86') }}
         uses: uraimo/run-on-arch-action@v2
         env:
           PYO3_USE_ABI3_FORWARD_COMPATIBILITY: 1