Update unittests.yml (#811)

Author: jGaboardi

.github/workflows/unittests.yml

@@ -32,9 +32,9 @@ jobs:
           - ci/313-dev.yaml
         include:
           - environment-file: ci/313-latest.yaml
-            os: macos-13 # Intel
+            os: macos-15-intel # Intel
           - environment-file: ci/313-latest.yaml
-            os: macos-14 # Apple Silicon
+            os: macos-latest # Apple Silicon
           - environment-file: ci/313-latest.yaml
             os: windows-latest
     defaults: