Fix xcbeautify repository reference in Mintfile

As the repository reference tuist/xcbeautify
does not have tagged version 2.3.0 due to
which 'mint bootstrap' was faliing.

Added correct reference for xcbeautify

Fixes issue ProtonMail#80

Mintfile

@@ -3,5 +3,5 @@ krzysztofzablocki/[email protected]
 mono0926/[email protected]
 realm/[email protected]
 SwiftGen/[email protected]
-tuist/[email protected]
+cpisciotta/[email protected]
 yonaskolb/[email protected]