Update Gutenberg Mobile reference with release tag

Author: fluiddot

build.gradle

@@ -13,7 +13,7 @@ ext {
     wordPressUtilsVersion = '2.7.0'
     wordPressLoginVersion = '0.19.0'
     aztecVersion = 'v1.6.0'
-    gutenbergMobileVersion = '5210-20d7e4c6eba8d46853379ce1bf4b061c61f22b83'
+    gutenbergMobileVersion = 'v1.84.0'
     storiesVersion = '1.4.0'
     aboutAutomatticVersion = '0.0.7'