Remove `AppendNewLine()` method

There already exists `AppendLineBreak()` method that does exactly the
same.

sources/Text/MutableText.uc

@@ -128,17 +128,6 @@ public final function MutableText AppendManyCharacters(
     return self;
 }
 
-/**
- *  Adds new line character to the end of the caller `MutableText`.
- *
- *  @return Caller `MutableText` to allow for method chaining.
- */
-public final function MutableText AppendNewLine()
-{
-    AppendCodePoint(CODEPOINT_NEWLINE);
-    return self;
-}
-
 /**
  *  Converts caller `MutableText` instance into lower case.
  */