Switch source-repository protocol to HTTPS

In order to pass `cabal check` (and upload this package to Hackage), we
need to update this protocol.

Author: jezen

http-reverse-proxy.cabal

@@ -71,4 +71,4 @@ test-suite test
 
 source-repository head
   type:     git
-  location: git://github.com/fpco/http-reverse-proxy.git
+  location: https://github.com/fpco/http-reverse-proxy.git