Use blackhole register when deleting lines

plug.vim

@@ -626,7 +626,7 @@ function! s:update_impl(pull, force, args) abort
     catch
       let lines = getline(4, '$')
       let printed = {}
-      silent 4,$d
+      silent 4,$d _
       for line in lines
         let name = get(matchlist(line, '^. \([^:]\+\):'), 1, '')
         if empty(name) || !has_key(printed, name)