Please delete 52.6.2esr related tags and branches from tor-browser.git

It turns out that I wrongly pushed tor-browser-52.6.2esr-7.5-1-build1, tor-browser-52.6.2esr-7.5-1, and tor-browser-52.6.2esr-7.5-2 to tor-browser.git a while ago. There has never been a planned ESR 52.6.2 release. Please remove those branches/tag as this is confusing.