import_export: Remove unused function `#git_bin_path`

The function `COmmandLineUtil#git_bin_path` isn't used anymore. Remove
it.

lib/gitlab/import_export/command_line_util.rb

@@ -95,10 +95,6 @@ module Gitlab
       end
       # rubocop:enable Gitlab/ModuleWithInstanceVariables
 
-      def git_bin_path
-        Gitlab.config.git.bin_path
-      end
-
       def copy_files(source, destination)
         # if we are copying files, create the destination folder
         destination_folder = File.file?(source) ? File.dirname(destination) : destination