Ouch! You're learning that lesson the hard way. Minutes of Council meetings should not be so specific as to single out an identifiable individual in this way, whether the allegations are fully proven or, as in this case, little more than hearsay. "Members expressed concern regarding the condition of a property in Acacia Way and resolved to report their concerns to..." or, if there are so few properties in Acacia Way that it's still easy to ascertain which property is under the spotlight, "... a property in the village..."
The GDPR situation is not straightforward. If we assume that the minutes of the meeting are an accurate record of the deliberations that took place, they should not be altered under the right to rectification, as they are not inaccurate (even though the information they contain was subsequently proved to be inaccurate). The right to erasure does not deal specifically with circumstances such as this and you could argue that you do not have to comply with this request. However, bearing in mind the particular circumstances of this case, my inclination would be to comply where it is reasonable and practical to do so.
Whatever you decide to do, remember that under the GDPR, you only have one calendar month from the date of the request to action it or notify rejection.