dont always use make if justfile is not found

only overwrite makeprg to just if justfile is found, otherwise default
to the default 'make' or whatever else makeprg was selected by the
compiler plugin

nvim/.config/nvim/init.lua

@@ -381,8 +381,6 @@ do
     end
     if look_for_file('justfile') then
         vim.go.makeprg = 'just'
-    else
-        vim.go.makeprg = 'make'
     end
 end