Update pubspec.yaml

Author: kainosk

Diff for: packages/firebase_core/pubspec.yaml

@@ -12,8 +12,7 @@ flutter:
     pluginClass: FirebaseCorePlugin
 
 dependencies:
-  flutter:
-    sdk: flutter
+  flutter_web:
   meta: "^1.0.5"
 
 dev_dependencies:
@@ -22,4 +21,4 @@ dev_dependencies:
 
 environment:
   sdk: ">=2.0.0-dev.28.0 <3.0.0"
-  flutter: ">=1.5.0 <2.0.0"
+#  flutter: ">=1.5.0 <2.0.0"