Rename variable master to implementation #2 (#2553)

(cherry picked from commit 103ff8e23d661972711245f814026b8812762f11)

contracts/mocks/ClonesMock.sol

@@ -11,16 +11,16 @@ contract ClonesMock {
 
     event NewInstance(address instance);
 
-    function clone(address master, bytes calldata initdata) public payable {
-        _initAndEmit(master.clone(), initdata);
+    function clone(address implementation, bytes calldata initdata) public payable {
+        _initAndEmit(implementation.clone(), initdata);
     }
 
-    function cloneDeterministic(address master, bytes32 salt, bytes calldata initdata) public payable {
-        _initAndEmit(master.cloneDeterministic(salt), initdata);
+    function cloneDeterministic(address implementation, bytes32 salt, bytes calldata initdata) public payable {
+        _initAndEmit(implementation.cloneDeterministic(salt), initdata);
     }
 
-    function predictDeterministicAddress(address master, bytes32 salt) public view returns (address predicted) {
-        return master.predictDeterministicAddress(salt);
+    function predictDeterministicAddress(address implementation, bytes32 salt) public view returns (address predicted) {
+        return implementation.predictDeterministicAddress(salt);
     }
 
     function _initAndEmit(address instance, bytes memory initdata) private {