patch 8.2.4005: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/help.c b/src/help.c
index 519edca..f07a8fc 100644
--- a/src/help.c
+++ b/src/help.c
@@ -104,7 +104,7 @@
     {
 #ifdef FEAT_MULTI_LANG
 	if (lang != NULL)
-	    semsg(_("E661: Sorry, no '%s' help for %s"), lang, arg);
+	    semsg(_(e_sorry_no_str_help_for_str), lang, arg);
 	else
 #endif
 	    semsg(_(e_sorry_no_help_for_str), arg);
@@ -1058,7 +1058,7 @@
 		    utf8 = this_utf8;
 		else if (utf8 != this_utf8)
 		{
-		    semsg(_("E670: Mix of help file encodings within a language: %s"), files[fi]);
+		    semsg(_(e_mix_of_help_file_encodings_within_language_str), files[fi]);
 		    mix = !got_int;
 		    got_int = TRUE;
 		}