Switch to macOS-15-intel instead

Author: Shimuuar

.github/workflows/ci.yml

@@ -35,6 +35,9 @@ jobs:
           - { cabal: "3.14", os: windows-latest, ghc: "9.10.2"  }
           - { cabal: "3.14", os: windows-latest, ghc: "9.12.2"  }
           # MacOS
+          - { cabal: "3.14", os: macOS-15-intel, ghc: "8.8.4"  }
+          - { cabal: "3.14", os: macOS-15-intel, ghc: "8.10.7" }
+          - { cabal: "3.14", os: macOS-15-intel, ghc: "9.0.2"  }
           - { cabal: "3.14", os: macOS-latest,   ghc: "9.2.8"  }
           - { cabal: "3.14", os: macOS-latest,   ghc: "9.4.8"  }
           - { cabal: "3.14", os: macOS-latest,   ghc: "9.6.7"  }