cleaned up gha

Author: matthewnitschke-wk

.github/workflows/dart_ci.yaml

@@ -16,7 +16,6 @@ jobs:
       fail-fast: false
       matrix:
         sdk:
-          - 2.13.4
           - 2.19.6
           # Commented out until we upgrade to Dart 3
           # - beta
@@ -37,7 +36,7 @@ jobs:
         run: dart run dependency_validator
       - name: Check formatting
         run: dart format --output=none --set-exit-if-changed .
-        if: ${{ matrix.sdk == 'stable' }}
+        if: ${{ matrix.sdk == '2.19.6' }}
       - name: Analyze project source
         run: dart analyze
       - name: Run tests