[ci] Remove null safety experiment flag (#24392)

Author: Casey Hillers

.cirrus.yml

@@ -55,7 +55,7 @@ task:
         bin/flutter analyze --dartdocs --flutter-repo --local-engine=host_debug_unopt
       test_framework_script: |
         cd $FRAMEWORK_PATH/flutter/packages/flutter
-        ../../bin/flutter test --local-engine=host_debug_unopt --null-assertions --sound-null-safety --enable-experiment=non-nullable
+        ../../bin/flutter test --local-engine=host_debug_unopt --null-assertions --sound-null-safety
     # TODO(fujino): remove this once ci/licenses.sh is run on LUCI
     - name: licenses_check
       build_script: |

ci/analyze.sh

@@ -62,7 +62,6 @@ echo "Analyzing dart:ui library..."
 autoninja -C "$SRC_DIR/out/host_debug_unopt" generate_dart_ui
 analyze \
   --options "$FLUTTER_DIR/analysis_options.yaml" \
-  --enable-experiment=non-nullable \
   "$SRC_DIR/out/host_debug_unopt/gen/sky/bindings/dart_ui/ui.dart"
 
 echo "Analyzing flutter_frontend_server..."