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/misc1.c b/src/misc1.c
index 3b265be..666cd58 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -2172,7 +2172,7 @@
 }
 
 /*
- * Function given to ExpandGeneric() to obtain an user names.
+ * Function given to ExpandGeneric() to obtain user names.
  */
     char_u*
 get_users(expand_T *xp UNUSED, int idx)