fix: simulator availability flake in firebasepod.yml (#15634)

Author: ncooke3

.github/workflows/firebasepod.yml

@@ -20,18 +20,22 @@ concurrency:
 
 jobs:
   installation-test:
-    # Don't run on private repo unless it is a PR.
-    if: (github.repository == 'Firebase/firebase-ios-sdk' && github.event_name == 'schedule') || github.event_name == 'pull_request'
-
+    if: github.repository == 'Firebase/firebase-ios-sdk'
     runs-on: macos-latest
-
     steps:
     - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
     - uses: ruby/setup-ruby@354a1ad156761f5ee2b7b13fa8e09943a5e8d252 # v1
     - name: Setup Bundler
       run: scripts/setup_bundler.sh
     - name: Xcode
       run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
+    - name: Install simulators in case they are missing.
+      uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 # v3
+      with:
+        timeout_minutes: 15
+        max_attempts: 5
+        retry_wait_seconds: 120
+        command: sudo xcodebuild -downloadPlatform iOS
     - name: Prereqs
       run: scripts/install_prereqs.sh FirebasePod iOS
     - name: Build