Vendored PHPMD binary issue.

[ulamthelucky]

I keep getting this error:

Warning: include(/usr/local/bin/../phpmd/phpmd/src/bin/phpmd): Failed to open stream: No such file or directory in /usr/local/bin/phpmd on line 119
Warning: include(): Failed opening '/usr/local/bin/../phpmd/phpmd/src/bin/phpmd' for inclusion (include_path='.:/usr/local/lib/php') in /usr/local/bin/phpmd on line 119

when trying to use this action with a vendored phpmd.

I submitted a PR that should fix that.