Exclude Rust extension testing for free-threaded Python

Free-threaded Python (3.13t) doesn't yet support Rust extensions via maturin.
Only test Rust with standard CPython 3.10.

Author: aclark4life

.github/workflows/test-python.yml

@@ -66,6 +66,9 @@ jobs:
           # Don't test Rust with pypy
           - python-version: "pypy-3.11"
             extension: "rust"
+          # Don't test Rust with free-threaded Python (not yet supported)
+          - python-version: "3.13t"
+            extension: "rust"
 
     name: CPython ${{ matrix.python-version }}-${{ matrix.os }}-${{ matrix.extension }}
     steps: