patch 9.1.0220: Few typos in source and test files

Problem:  Typos in code and tests.
Solution: Fix typos (zeertzjq).

closes: #14321

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_buffer.vim b/src/testdir/test_buffer.vim
index bc29c21..a5643b3 100644
--- a/src/testdir/test_buffer.vim
+++ b/src/testdir/test_buffer.vim
@@ -133,7 +133,7 @@
   call assert_fails('1,1bdelete 1 2', 'E488:')
   call assert_fails('bdelete \)', 'E55:')
 
-  " Deleting a unlisted and unloaded buffer
+  " Deleting an unlisted and unloaded buffer
   edit Xbdelfile1
   let bnr = bufnr()
   set nobuflisted