util: remove the copypasta unquote function The _urlunquote function was added back in the day to improve startup performance, but this version is a) not compatible with Python 3 and b) has quadratic performance issues that Python core solved eons ago. Moreover, the function moved from urllib to urlparse (cheaper to import) *and* that module is already imported into pycompat. As a result, removing this function improves perf now. Before: ! wall 0.066773 comb 0.000000 user 0.000000 sys 0.000000 (best of 100) After: ! wall 0.065990 comb 0.000000 user 0.000000 sys 0.000000 (best of 100)