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_history.vim b/src/testdir/test_history.vim
index 482328a..19490f2 100644
--- a/src/testdir/test_history.vim
+++ b/src/testdir/test_history.vim
@@ -254,7 +254,7 @@
   set key& bs& ts&
 endfunc
 
-" The following used to overflow and causing an use-after-free
+" The following used to overflow and causing a use-after-free
 func Test_history_max_val()
 
   set history=10