(build) Update what build runners are used

Ubuntu 18.04 is out of support, and Cake.Git doesn't work on the latest
version of macOS (which is the M1 variant), so need to pin to the latest
within the 13 range.

.github/workflows/build.yaml

@@ -11,7 +11,11 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [windows-latest, ubuntu-18.04, macos-latest]
+        os: [
+          windows-latest,
+          ubuntu-latest,
+          # Cake.Recipe currently does not support macOS 14 (M1) due to usage of Cake.Git.
+          macos-13]
 
     steps:
       - uses: actions/[email protected]