Simplify/fix dart formatting in CI

.github/workflows/flutterfmt.sh

@@ -1,10 +0,0 @@
-#!/bin/sh
-DIRS="lib test"
-EXIT=0
-
-for DIR in $DIRS; do
-    OUT="$(dart format -l 120 --suppress-analytics "$DIR" | sed -e "s/^Formatted \(.*\)/::error file=$DIR\/\1::Not formatted/g")"
-    echo "$OUT" | grep "::error" && EXIT=1
-done
-
-exit $EXIT

.github/workflows/flutterfmt.yml

@@ -23,5 +23,5 @@ jobs:
       - name: Check out code
         uses: actions/checkout@v3
 
-      - name: flutter format
+      - name: Check formating
-        run: $GITHUB_WORKSPACE/.github/workflows/flutterfmt.sh
+        run: dart format -l120 lib/ test/ --set-exit-if-changed --suppress-analytics