patch 8.2.3961: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index 73c5a91..9468beb 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -2903,7 +2903,7 @@
     pat = tv_get_string(&argvars[0]);
     if (argvars[1].v_type != VAR_STRING)
     {
-	semsg(_(e_invarg2), "type must be a string");
+	semsg(_(e_invalid_argument_str), "type must be a string");
 	return;
     }
     type = tv_get_string(&argvars[1]);
@@ -2933,7 +2933,7 @@
 	xpc.xp_context = cmdcomplete_str_to_type(type);
 	if (xpc.xp_context == EXPAND_NOTHING)
 	{
-	    semsg(_(e_invarg2), type);
+	    semsg(_(e_invalid_argument_str), type);
 	    return;
 	}