ci: update github macos-x86 runner

Author: sobuch

.github/workflows/build_openocd.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   build-macos-x86:
-    runs-on: macos-13
+    runs-on: macos-15-intel
     steps:
       - name: Ensure architecture is x86_64
         run: |

.github/workflows/test_openocd.yml

@@ -6,7 +6,7 @@ on:
 jobs:
   run-macos-x86-host:
     name: Test OpenOCD on MacOS-x86
-    runs-on: macos-13
+    runs-on: macos-15-intel
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4