vim-patch:8.2.2231: when "--remote file" is used "file" is not reloaded

Problem:    When "--remote file" is used "file" is not reloaded.
Solution:   When a :drop command is used for a file that is already displayed
            in a window and it has not been changed, check if it needs to be
            reloaded. (closes vim/vim#7560)
e4862a0fe6

Remove unused "focus" parameter from "buf_check_timestamp()".
It was meant for removed GUI code.

src/nvim/diff.c

@@ -805,7 +805,7 @@ static void diff_try_update(diffio_T    *dio,
     for (idx_new = idx_orig; idx_new < DB_COUNT; idx_new++) {
       buf = curtab->tp_diffbuf[idx_new];
       if (buf_valid(buf)) {
-        buf_check_timestamp(buf, false);
+        buf_check_timestamp(buf);
       }
     }
   }