patch 8.2.3967: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/session.c b/src/session.c
index e64697f..fdda5ee 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1298,7 +1298,7 @@
 			|| ((ssop_flags & SSOP_CURDIR) && globaldir != NULL)))
 		    {
 			if (mch_chdir((char *)dirnow) != 0)
-			    emsg(_(e_prev_dir));
+			    emsg(_(e_cannot_go_back_to_previous_directory));
 			shorten_fnames(TRUE);
 		    }
 		    vim_free(dirnow);