Reduce the testing matrix to just one

Signed-off-by: Jose Luis Rivero <jrivero@honurobotics.com>

Author: j-rivero

.github/workflows/ci.yaml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.11', '3.12', '3.13']
+        python-version: ['3.13']
     name: Test empy < 4 compatibility (Python ${{ matrix.python-version }})
     steps:
       - uses: actions/checkout@v4