title: How to downgrade packages in flutter?
body: <p>cloud_firestore 0.12.11 isn't working for me in flutter, it won't allow my app to launch in debug. How would i downgrade this package? In the pubspec file I used a lower version of cloud_firestore ie. (cloud_firestore: ^0.12.9+4) and then saved and VS Code got the packages but when I try to launch again it gives the same error : </p>
  
  <pre><code>                     ~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      /Users/kev/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore- 
      0.12.11/ios/Classes/CloudFirestorePlugin.m:157:24: error: no visible @interface for 
      'FIRQuery' declares the selector 'queryWhereFieldPath:arrayContainsAny:'
                  query = [query queryWhereFieldPath:fieldPath arrayContainsAny:value];
                       ~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      /Users/kev/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore- 
     0.12.11/ios/Classes/CloudFirestorePlugin.m:163:24: error: no visible @interface for 
     'FIRQuery' declares the selector 'queryWhereField:in:'
              query = [query queryWhereField:fieldName in:value];
                       ~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      /Users/kev/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore- 
     0.12.11/ios/Classes/CloudFirestorePlugin.m:165:24: error: no visible @interface for 
    'FIRQuery' declares the selector 'queryWhereFieldPath:in:'
                  query = [query queryWhereFieldPath:fieldPath in:value];
                       ~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      /Users/kev/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore- 
     0.12.11/ios/Classes/CloudFirestorePlugin.m:764:16: warning: 'timestampsInSnapshotsEnabled' 
      is deprecated [-Wdeprecated-declarations]
                settings.timestampsInSnapshotsEnabled = 
      (bool)call.arguments[@"timestampsInSnapshotsEnabled"];
                     ^
      In module 'FirebaseFirestore' imported from 
  
    /Users/kev/Documents/flutterprojects/shopapp/ios/Pods/Headers/Public/Firebase/Firebase.h:45:
  
   /Users/kev/Documents/flutterprojects/shopapp/ios/Pods/FirebaseFirestore/Firestore/Source/Public .   /FIRFirestoreSettings.h:69:20: note: 'timestampsInSnapshotsEnabled' has been explicitly marked 
      deprecated here
             __attribute__((deprecated));
                         ^
         1 warning and 4 errors generated.
         note: Using new build systemnote: Planning buildnote: Constructing build description
     Could not build the application for the simulator.
     Error launching application on iPhone X.
  </code></pre>
  
  <p><strong>When i checked the flutter SDK inside of the .pubcache -> hosted -> pub.dartlang.org -> there is a folder in there cloud_firestore 0.12.11</strong> how do i fix this? my applicatoin starts fine when i launch with cloud_firestore commented out in the pubspec file.</p>