Simplify CI matrix to stable Python 3.10 baseline

- Remove Python 3.11 and 3.12 jobs
- Drop NumPy 2.x combinations
- Keep Python 3.10 + NumPy 1.26.4 only

Author: adilraza99

.github/workflows/tests.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        python-version: ["3.10", "3.11"]
+        python-version: ["3.10"]
         numpy-version: ["numpy==1.26.4"]
     runs-on: ubuntu-latest