Greater Manchester Police is cancelling leave for many of its officers this weekend as it steps up patrols to oversee the reopening of pubs and prevent further illegal raves.A ‘significant operation’ is planned across the region on Saturday July 4, the day when bars and restaurants will open for the first time in more than three months.Mayor Andy Burnham says there will be an increased police presence in cities and towns but the force’s approach will not be ‘heavy handed’.He said: "GMP will have