Update DMS "Translation Center" link: from 404 to Transifex

From 404 to the DMS Transifex translation project.

Ref. https://github.com/pagelines/DMS/tree/1.1/language/readme.txt

"********************************************************

	PageLines I18n
	==============
	
	Join our translation task force at
	www.transifex.com/projects/p/pagelines-dms/

********************************************************

support-troubleshooting/getting-support.md

@@ -36,7 +36,7 @@ The PageLines [Issue Tracker](https://github.com/pagelines/DMS/issues) should be
 
 ### Translation Center ###
 
-The PageLines [Translation Center](http://pagelines.com/translate/projects/) allows PageLines users and developers to collaborate on translations.
+The PageLines [Translation Center](https://www.transifex.com/projects/p/pagelines-dms/) allows PageLines users and developers to collaborate on translations.
 
 ### PageLines Pastie ###