patch 8.2.4680: build failure without +postscript

Problem:    Build failure without +postscript.
Solution:   Use another error message.
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 483fe1e..6303cc1 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -2637,7 +2637,7 @@
 			if (do_source(si->sn_name, FALSE, DOSO_NONE, NULL)
 								       == FAIL)
 			{
-			    semsg(_(e_cant_open_file_str_2), si->sn_name);
+			    semsg(_(e_cant_open_file_str), si->sn_name);
 			    goto on_error;
 			}
 		    }