Update plugin readme

Author: wtfsayo

packages/plugin-near/README.md

@@ -35,7 +35,7 @@ NEAR_WALLET_PUBLIC_KEY=your-wallet-public-key
 NEAR_ADDRESS=your-account.near
 NEAR_NETWORK=testnet  # mainnet or testnet
 NEAR_RPC_URL=https://rpc.testnet.near.org
-SLIPPAGE=0.01  # 1% slippage tolerance
+NEAR_SLIPPAGE=0.01  # 1% slippage tolerance
 ```
 
 ## Usage