search.config.js: Update spec URL

In what can only be described as an act of pure benevolence,
@alloy moved all .podspec files in CocoaPods/Specs into a subdirectory,
thereby saving thousands from unnecessarily long load times.

https://github.com/CocoaPods/Specs/commit/b947340d648f51d66a6df1cbd1b5f7d8cf5a6de0

Surely, the need to change each spec's URL is a trivial price to pay in
order to enjoy such a change.