travis: remove empty vm tests

Author: alextekartik

tool/travis.dart

@@ -9,7 +9,8 @@ Future main() async {
   dartanalyzer --fatal-warnings --fatal-infos .
   dartfmt -n --set-exit-if-changed .
 
-  pub run test -p vm -j 1
+  # No VM tests
+  # pub run test -p vm -j 1
   # pub run build_runner test -- -p vm -j 1 test/multiplatform
   
   pub run test -p chrome -j 1