Fix character literal (#383)

Previously the character literal was updated
mimicking that of Rust apparently,
but Scala doesn't have curly braces in the character literal.

We do, however, support two 'u' characters.

Author: eed3si9n

corpus/literals.txt

@@ -228,6 +228,8 @@ val myChar = 'c'
 
 val otherChar = '\u0041'
 
+val otherChar2 = '\uu0041'
+
 val anotherChar = '\n'
 
 def foo(a: Char = 'c') = a + 'd'
@@ -244,6 +246,9 @@ def foo(a: Char = 'c') = a + 'd'
   (val_definition
     (identifier)
     (character_literal))
+  (val_definition
+    (identifier)
+    (character_literal))
   (function_definition
     (identifier)
     (parameters

grammar.js

@@ -1554,8 +1554,7 @@ module.exports = grammar({
                 "\\",
                 choice(
                   /[^xu]/,
-                  /u[0-9a-fA-F]{4}/,
-                  /u{[0-9a-fA-F]+}/,
+                  /uu?[0-9a-fA-F]{4}/,
                   /x[0-9a-fA-F]{2}/,
                 ),
               ),