Wolfram Programming Cloud is now Wolfram Development Platform, see for example Wolfram Cloud. Who can add this synonym to the Wolfram Programming Cloud tag?
I suggest replacing wolfram-programming-cloud with wolfram-cloud, as the differences between the Development Platform and Mathematica Online are neglectable with respect to the Wolfram Language code used within these.
As to how synonyms work the system says:
Users with more than 2500 reputation and a total answer score of 5 or more on the tag, can suggest tag synonyms. Users with a total answer score (total upvotes minus total downvotes) of 5 or more on the tag, can vote for tag synonyms. Suggestions will be automatically approved when they reach a score of 4, and automatically deleted when they reach a score of -2.
Community moderators are able to directly apply synonyms and merges.