patch 8.2.3985: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/regexp.c b/src/regexp.c
index 9e3d218..fdcd6d1 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -66,7 +66,7 @@
 #define EMSG2_RET_NULL(m, c) return (semsg((const char *)(m), (c) ? "" : "\\"), rc_did_emsg = TRUE, (void *)NULL)
 #define EMSG3_RET_NULL(m, c, a) return (semsg((const char *)(m), (c) ? "" : "\\", (a)), rc_did_emsg = TRUE, (void *)NULL)
 #define EMSG2_RET_FAIL(m, c) return (semsg((const char *)(m), (c) ? "" : "\\"), rc_did_emsg = TRUE, FAIL)
-#define EMSG_ONE_RET_NULL EMSG2_RET_NULL(_("E369: invalid item in %s%%[]"), reg_magic == MAGIC_ALL)
+#define EMSG_ONE_RET_NULL EMSG2_RET_NULL(_(e_invalid_item_in_str_brackets), reg_magic == MAGIC_ALL)
 
 
 #define MAX_LIMIT	(32767L << 16L)