Revert "chore(CI): update CI to use {macos,gcc}-latest"

This reverts commit 82c0cd3.

Author: rouson

.github/workflows/cmake.yml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest]
         toolchain:
-          - {compiler: gcc, version: 14}
+          - {compiler: gcc, version: 11}
           - {compiler: intel-classic, version: '2021.9'}
         include:
           - os: ubuntu-latest

.github/workflows/fpm.yml

@@ -8,13 +8,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest]
-        gcc_v: [14] # Version of GFortran we want to use.
+        os: [ubuntu-latest, macos-11]
+        gcc_v: [10] # Version of GFortran we want to use.
         include:
         - os: ubuntu-latest
           os-arch: linux-x86_64
 
-        - os: macos-latest
+        - os: macos-11
           os-arch: macos-x86_64
 
     env: