patch 8.1.0851: feedkeys() with "L" does not work properly

Problem:    feedkeys() with "L" does not work properly.
Solution:   Do not set typebuf_was_filled when using "L". (Ozaki Kiichi,
            closes #3885)
diff --git a/src/testdir/test_mapping.vim b/src/testdir/test_mapping.vim
index 921b693..c454fc0 100644
--- a/src/testdir/test_mapping.vim
+++ b/src/testdir/test_mapping.vim
@@ -215,7 +215,7 @@
   set timeout timeoutlen=1000
 
   func ExitCb(job, status)
-    let g:timer = timer_start(1, {_ -> feedkeys("3\<Esc>", 't')})
+    let g:timer = timer_start(1, {-> feedkeys("3\<Esc>", 't')})
   endfunc
 
   call job_start([&shell, &shellcmdflag, 'echo'], {'exit_cb': 'ExitCb'})