tests: fix a stale reference to experimental.uncommitondirtywdir
These tests no longer test the config option, they test the command
line flag.
Differential Revision: https://phab.mercurial-scm.org/D6077
--- a/tests/test-uncommit.t Thu Feb 28 01:49:10 2019 +0100
+++ b/tests/test-uncommit.t Wed Mar 06 15:35:40 2019 -0800
@@ -469,7 +469,7 @@
a
$ cd ..
-experimental.uncommitondirtywdir should also work on a dirty PATH
+--allow-dirty-working-copy should also work on a dirty PATH
$ hg init issue5977
$ cd issue5977