。
Stop putting on airs.
Literal
Being-pretentious [nom-の] [topic-は] stop [request-くれ].
勿体振る (もったいぶる) means 'to be pretentious, put on airs, act coy.' The ~のはやめてくれ pattern combines nominalization (~のは) with やめる ('stop') and ~てくれ ('do for me' as a blunt request). Forceful and direct.