ci:macos: disable GCC for now as generally broken on GHA

Author: scivision

.github/workflows/ci.yml

@@ -105,7 +105,9 @@ jobs:
 
     strategy:
       matrix:
-        c: [{cc: clang, cxx: clang++}, {cc: gcc-13, cxx: g++-13}]
+        c: [{cc: clang, cxx: clang++}]
+
+    # {cc: gcc-13, cxx: g++-13}  macos GHA broken in general for GCC
 
     env:
       FC: gfortran-13