fixed non-standard version spec in package.json causing podspec installation to fail

[!] Invalid `Podfile` file:
[!] Invalid `RNFirebaseUi.podspec` file: Malformed version number string v0.1.2.

 #  from /Users/hein/repos/scratch/RN61/node_modules/react-native-firebaseui/RNFirebaseUi.podspec:15
 #  -------------------------------------------
 #
 >    s.source       = { :git => "https://github.com/rmrs/react-native-firebaseui.git", :tag => "#{s.version}" }
 #    s.source_files  = "ios/**/*.{h,m}"
 #  -------------------------------------------

Author: IjzerenHein

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-native-firebaseui",
-  "version": "v0.1.2",
+  "version": "0.1.2",
   "description": "React Native Firebase Bindings Based on FirebaseUI SDK",
   "main": "index.js",
   "repository": {