Update tools/setup-vendor-flutter

Co-authored-by: Greg Price <[email protected]>

Author: chrisirhc

tools/setup-vendor-flutter

@@ -11,7 +11,7 @@ this_dir=${BASH_SOURCE[0]%/*}
 # using the main channel (main branch).
 # We should do a quick check that there's no changes.
 if ! submodule_is_clean "vendor/flutter" ; then
-    echo >&2 "There are changes in 'vendor/flutter' tree or it is not initialized."
+    echo >&2 "There are changes in the 'vendor/flutter' tree or it is not initialized."
     echo >&2 "Please run 'git submodule update --init' then run this script again."
     exit 1
 fi