update test setp as suggested

Author: AlaaElattar

packages/tfchain_client/README.md

@@ -53,8 +53,7 @@ dart run polkadart_cli:generate -v
 
 ### Prerequisites
 
-1- To run the tests a local docker image of the TFChain :
-
+1- To run the tests against a local docker image of the TFChain:
 ```bash
 docker run --network host ghcr.io/threefoldtech/tfchain:2.8.1 --dev --rpc-cors all --rpc-external --rpc-methods=safe
 ```