patch 8.2.4012: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move the last error messages to errors.h.
diff --git a/src/syntax.c b/src/syntax.c
index 36f3510..f4d7f1d 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -4889,8 +4889,8 @@
 			{
 			    if (p[2] != NUL)
 			    {
-				semsg(_("E890: trailing char after ']': %s]%s"),
-								kw, &p[2]);
+				semsg(_(e_trailing_char_after_rsb_str_str),
+								    kw, &p[2]);
 				goto error;
 			    }
 			    kw = p + 1;		// skip over the "]"