Update build_testapps to use ndk r21

Author: a-maurice

scripts/gha/build_testapps.py

@@ -504,12 +504,12 @@ def patch_android_env(unity_version):
   # Set ndk env
   UNITY_SETTINGS = {
     "2022": {
-      _WINDOWS: "https://dl.google.com/android/repository/android-ndk-r19-windows-x86_64.zip",
-      _MACOS: "https://dl.google.com/android/repository/android-ndk-r19-darwin-x86_64.zip",
+      _WINDOWS: "https://dl.google.com/android/repository/android-ndk-r21-windows-x86_64.zip",
+      _MACOS: "https://dl.google.com/android/repository/android-ndk-r21-darwin-x86_64.zip",
     },
     "2021": {
-      _WINDOWS: "https://dl.google.com/android/repository/android-ndk-r19-windows-x86_64.zip",
-      _MACOS: "https://dl.google.com/android/repository/android-ndk-r19-darwin-x86_64.zip",
+      _WINDOWS: "https://dl.google.com/android/repository/android-ndk-r21-windows-x86_64.zip",
+      _MACOS: "https://dl.google.com/android/repository/android-ndk-r21-darwin-x86_64.zip",
     },
     "2020": {
       _WINDOWS: "https://dl.google.com/android/repository/android-ndk-r19-windows-x86_64.zip",