Update the set of OSX runners since github removed 10.15

Author: TheBlueMatt

.github/workflows/build.yml

@@ -110,8 +110,9 @@ jobs:
     strategy:
       matrix:
         include:
-          - platform: macos-10.15
           - platform: macos-11
+          - platform: macos-12
+          - platform: macos-13
     runs-on: ${{ matrix.platform }}
     env:
       TOOLCHAIN: stable