fix revert messages

Author: ItsNickBarry

spec/token/ERC20/ERC20Base.behavior.ts

@@ -238,7 +238,7 @@ export function describeBehaviorOfERC20Base(
                 receiver.address,
                 amount,
               ),
-          ).to.be.revertedWith('ERC20: transfer amount exceeds allowance');
+          ).to.be.revertedWith('ERC20: insufficient allowance');
         });
       });
     });

spec/token/ERC20/ERC20Extended.behavior.ts

@@ -164,7 +164,7 @@ export function describeBehaviorOfERC20Extended(
                 spender.address,
                 ethers.constants.One,
               ),
-          ).to.be.revertedWith('ERC20Extended: insufficient allowance');
+          ).to.be.revertedWith('ERC20: insufficient allowance');
         });
       });
     });