Change mini.statusline location format to LINE:COLUMN (nvim-lua#659)

Default mini.statusline location format is:
  'cursor line | total lines │ cursor column | total columns'

init.lua

@@ -762,6 +762,9 @@ require('lazy').setup {
       --  You could remove this setup call if you don't like it,
       --  and try some other statusline plugin
       require('mini.statusline').setup()
+      MiniStatusline.section_location = function()
+        return '%2l:%-2v'
+      end
 
       -- ... and there is more!
       --  Check out: https://github.com/echasnovski/mini.nvim