Park in up market suburb of Giffnock in East Renfrewshire causing outrage among locals.But yesterday a note in a plastic 'polly pocket' was left pinned near the scene in the town.Addressed to the 'Dear residents of Giffnock' the youngsters unreservedly apologise for their behaviour in the park.And they have been praised and forgiven by locals for their 'maturity'.The letter, seen by the Record, reads: "We saw your Facebook post and wanted to say how sorry we are for the mess we left last