ci: remove macOS-15 machine

Author: rinsuki

.github/workflows/archive.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         xcode: ["26.0"]
         os: ["iOS"]
-        machine: ["macOS-15", "macOS-26"]
+        machine: ["macOS-26"]
     runs-on: ${{ matrix.machine }}
     steps:
     - uses: actions/checkout@v4

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
           - macOS
           - iOS
           - visionOS
-        machine: ["macOS-15", "macOS-26"]
+        machine: ["macOS-26"]
     runs-on: ${{ matrix.machine }}
     steps:
     - uses: actions/checkout@v1