To remove Liquidity from Liquidity Mining, please go to your Liquidity Mining Page, scroll down until you see "My Liquidity", and then you can on the right side of the pool under "Actions", click "Remove".
Please note, when adding/removing liquidity, the bar "DEX-market price stability" -> if that is not stabilized, you can enter or leave with fewer coins in/out of the liquidity mining, and thereby getting less coins than shown to you.
For more information regarding Liquidity Mining, please check the following article: What is Liquidity Mining?