Add explicit comment on transaction types that do not update the sign…

…er nonce

Signed-off-by: Stoyan Panayotov <[email protected]>

HIP/hip-844.md

@@ -45,7 +45,7 @@ message ContractFunctionResult {
 
     /**
      * If not null this field specifies what the value of the signer account nonce is post transaction execution. 
-     * For transactions that don't update the signer nonce, this field should be null.
+     * For transactions that don't update the signer nonce (like HAPI ContractCall and ContractCreate transactions) this field should be null.
      */
     Int64Value signer_nonce = 15;
 }