Escape a $ symbol in help message and rephrase slightly. Without this,
`php maintenance/language/checkDupeMessages.php --help` prints
PHP Notice: Undefined variable: dupeMessages in
language/checkDupeMessages.php on line 56
Change-Id: Ie7c0f07e68cee1f7cd2758f71b09d34e339d4b7b
* mode: Output format, can be either:
* text: Text output on the console (default)
* wiki: Wiki format, with * at beginning of each line
- * php: Output text as PHP syntax in a array $dupeMessages
+ * php: Output text as PHP syntax in an array named \$dupeMessages
* raw: Raw output for duplicates
TEXT;
}