Update Core version to 4.0.2 (firebase#76)

Author: paulb777

Firebase/Core/FIROptions.m

@@ -42,7 +42,7 @@
 NSString *const kFIRLibraryVersionID =
     @"4"     // Major version (one or more digits)
     @"00"    // Minor version (exactly 2 digits)
-    @"01"    // Build number (exactly 2 digits)
+    @"02"    // Build number (exactly 2 digits)
     @"000";  // Fixed "000"
 // Plist file name.
 NSString *const kServiceInfoFileName = @"GoogleService-Info";