Edit Installation from git://github.com to https://github.com

[eiger3970]

Installation -> With pathogen.vim: -> command -> please update the command git clone git://github.com/will133/vim-dirdiff to git clone https://github.com/will133/vim-dirdiff

[smemsh]

see #49 which fixes this. it's because github removed support for unencrypted url schemes in march 2022.