Bump release to use 3.16.6 (#5886)

google_maps_flutter_ios now requires 3.16.6, so we need to bump the release script so that it can be published by CI.

Fixes the tree.

Author: stuartmorgan-g

.github/workflows/release.yml

@@ -31,7 +31,7 @@ jobs:
       # the change if it doesn't.
       run: |
         cd $HOME
-        git clone https://github.com/flutter/flutter.git --depth 1 -b 3.16.0 _flutter
+        git clone https://github.com/flutter/flutter.git --depth 1 -b 3.16.6 _flutter
         echo "$HOME/_flutter/bin" >> $GITHUB_PATH
         cd $GITHUB_WORKSPACE
     # Checks out a copy of the repo.