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/dict.c b/src/dict.c
index b49005a..6773c75 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -720,7 +720,7 @@
 	return 0;
     if (di->di_tv.v_type != VAR_NUMBER)
     {
-	semsg(_(e_invarg2), tv_get_string(&di->di_tv));
+	semsg(_(e_invalid_argument_str), tv_get_string(&di->di_tv));
 	return 0;
     }
     return tv_get_number(&di->di_tv);
@@ -1257,7 +1257,7 @@
 		    break;
 	    if (i == 3)
 	    {
-		semsg(_(e_invarg2), action);
+		semsg(_(e_invalid_argument_str), action);
 		return;
 	    }
 	}