patch 9.1.0375: tests: 1-second delay after Test_BufEnter_botline()

Problem:  tests: 1-second delay after Test_BufEnter_botline()
          (after v9.1.0374)
Solution: Wipe the created buffers (zeertzjq).

closes: #14647

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 6745ecb..24e1daf 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -4687,6 +4687,9 @@
   edit Xxx2
   au BufEnter Xxx1 call assert_true(line('w$') > 1)
   edit Xxx1
+
+  bwipe! Xxx1
+  bwipe! Xxx2
   au! BufEnter Xxx1
   set hidden&vim
 endfunc