fix: deduct taxAmount from msg.value to preserve it in contracts' balance

This change adjust the value passed to the createDispute function to ensure that the contract's balance accurately reflects the dudcted tax amount, maintaining proper accounting.

Author: gratestas

contracts/TruthPost.sol

@@ -142,18 +142,17 @@ contract TruthPost is ITruthPost, IArbitrable, IEvidence {
     /// @inheritdoc ITruthPost
     function challenge(uint80 _articleStorageAddress) external payable override {
         Article storage article = articleStorage[_articleStorageAddress];
+        require(article.bountyAmount > 0, "Nothing to challenge.");
         require(article.withdrawalPermittedAt != type(uint32).max, "There is an ongoing challenge.");
         article.withdrawalPermittedAt = type(uint32).max;
         // Mark as challenged.
 
         require(msg.value >= challengeFee(_articleStorageAddress), "Insufficient funds to challenge.");
 
-        treasuryBalance += ((uint96(article.bountyAmount) << NUMBER_OF_LEAST_SIGNIFICANT_BITS_TO_IGNORE) * challengeTaxRate) / MULTIPLIER_DENOMINATOR;
-
-        // To prevent mistakes.
-        require(article.bountyAmount > 0, "Nothing to challenge.");
+        uint taxAmount = ((uint96(article.bountyAmount) << NUMBER_OF_LEAST_SIGNIFICANT_BITS_TO_IGNORE) * challengeTaxRate) / MULTIPLIER_DENOMINATOR;
+        treasuryBalance += taxAmount;
 
-        uint256 disputeID = ARBITRATOR.createDispute{value : msg.value}(NUMBER_OF_RULING_OPTIONS, categoryToArbitratorExtraData[article.category]);
+        uint256 disputeID = ARBITRATOR.createDispute{value :  msg.value - taxAmount }(NUMBER_OF_RULING_OPTIONS, categoryToArbitratorExtraData[article.category]);
 
         disputes[disputeID].challenger = payable(msg.sender);
         disputes[disputeID].rounds.push();