It would be quite wrong to attempt to modify minutes to eliminate a decision that was actually taken. However, the six month limit is not statutory, it is simply a commonly used standing order. The council can vote to suspend that order in relation to the issue in question, immediately before reconsidering the decision. It can do this at any time.
The purpose of the six month rule is to stop councillors from repeatedly raising the same issue when the council has no wish to do so. It is only binding while the council wishes it to be.