Yes, you can sell your pledged holding. Once you sell your pledged holding, it'll be unpledged and sold. You'll no longer receive the pledge margin benefit for that particular holding, and the same will be reduced from your Groww pledged balance.
Please note: If you have a negative Groww balance, please clear it by adding money to your Groww balance before selling the pledged stocks. If you sell your pledged stocks while you have a negative balance, funds received after selling the holdings will be used to recover the negative balance.