fix: remove unsupported --fix flag from dart format in melos scripts

Dart 3.11 no longer supports the --fix flag on dart format.
This was causing the CI format-check step to fail.

Author: lijy91

melos.yaml

@@ -23,11 +23,11 @@ scripts:
         - test
 
   format:
-    exec: dart format . --fix
+    exec: dart format .
     description: Run `dart format` for all packages.
 
   format-check:
-    exec: dart format . --fix --set-exit-if-changed
+    exec: dart format . --set-exit-if-changed
     description: Run `dart format` checks for all packages.
 
   fix: