Optimize gas fee (#401)

* optimize gas fee

* remove unchecked iterator increments

* formatting my code

* format my code

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Co-authored-by: HuyHuynh3103 <1917420@student.hcmus.edu.vn>

contracts/src/v0.1/VRFCoordinator.sol

@@ -162,9 +162,10 @@ contract VRFCoordinator is
             revert NoSuchProvingKey(kh);
         }
         delete s_provingKeys[kh];
-        for (uint256 i = 0; i < s_provingKeyHashes.length; i++) {
+        uint256 provingKeyHashesLength = s_provingKeyHashes.length;
+        for (uint256 i; i < provingKeyHashesLength; i++) {
             if (s_provingKeyHashes[i] == kh) {
-                bytes32 last = s_provingKeyHashes[s_provingKeyHashes.length - 1];
+                bytes32 last = s_provingKeyHashes[provingKeyHashesLength - 1];
                 // Copy last element and overwrite kh to be deleted with it
                 s_provingKeyHashes[i] = last;
                 s_provingKeyHashes.pop();