.github/workflows: cope with end of life of macos-13.

We change all occurrencies of macos-13 to macos-15-intel.

Author: julian-smith-artifex-com

.github/workflows/build_wheels.yml

@@ -84,8 +84,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        # 2024-05-08: Need to specify macos-13/14 to get x86_64/arm64.
-        os: [ubuntu-latest, windows-2019, macos-13, macos-14]
+        # 2024-05-08: Need to specify macos-15-intel/14 to get x86_64/arm64.
+        os: [ubuntu-latest, windows-2019, macos-15-intel, macos-14]
 
       # Avoid cancelling of all cibuildwheel runs after a single failure.
       fail-fast: false

.github/workflows/test.yml

@@ -26,7 +26,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, windows-2022, macos-13, macos-14]
+        os: [ubuntu-latest, windows-2022, macos-15-intel, macos-14]
 
       # Avoid cancelling of all runs after a single failure.
       fail-fast: false

.github/workflows/test_multiple.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, windows-2022, macos-13, macos-14]
+        os: [ubuntu-latest, windows-2022, macos-15-intel, macos-14]
         args: [
             '',
             '-m "git:--branch master https://github.com/ArtifexSoftware/mupdf"',