[Infra] Move 'firebasepod' workflow to Xcode 16 (#14693)

Author: ncooke3

.github/workflows/firebasepod.yml

@@ -34,7 +34,7 @@ jobs:
     - name: Setup Bundler
       run: scripts/setup_bundler.sh
     - name: Xcode
-      run: sudo xcode-select -s /Applications/Xcode_15.4.app/Contents/Developer
+      run: sudo xcode-select -s /Applications/Xcode_16.2.app/Contents/Developer
     - name: Prereqs
       run: scripts/install_prereqs.sh FirebasePod iOS
     - name: Build