patch 9.1.1319: Various typos in the code, issue with test_inst_complete.vim

Problem:  Various typos in the code, redundant and strange use of
          :execute in test_ins_complete.vim (after 9.1.1315).
Solution: Fix typos in the code and in the documentation, use the
          executed command directly (zeertzjq).

closes: #17143

Co-authored-by: Christ van Willegen <cvwillegen@gmail.com>
Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/quickfix.c b/src/quickfix.c
index 2b12fb5..2bc2f2d 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -119,7 +119,7 @@
 };
 
 static qf_info_T ql_info_actual; // global quickfix list
-static qf_info_T *ql_info;	// points to ql_info_actual if memory allocation is sucessful.
+static qf_info_T *ql_info;	// points to ql_info_actual if memory allocation is successful.
 static int_u last_qf_id = 0;	// Last used quickfix list id
 
 #define FMT_PATTERNS 14		// maximum number of % recognized