CI: bump numpy to v1.26 for testing

Author: dmgav

.github/workflows/testing.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         host-os: ["ubuntu-latest", "macos-latest", "windows-latest"]
         python-version: ["3.9", "3.10", "3.11"]
-        numpy-version: ["1.24"]
+        numpy-version: ["1.26"]
         pyqt-version: ["5.15"]
         include:
           - host-os: "ubuntu-latest"