tests: fix config knob in test-narrow-clone-stream.t

tests: fix config knob in test-narrow-clone-stream.t

Two patches landed in parallel and had a semantic conflict. This
resolves the mess and leaves us with passing tests.

Differential Revision: https://phab.mercurial-scm.org/D5231

--- a/tests/test-narrow-clone-stream.t	Tue Nov 06 10:26:33 2018 -0500
+++ b/tests/test-narrow-clone-stream.t	Tue Nov 06 10:41:00 2018 -0500
@@ -36,8 +36,8 @@
 
 Enable stream clone on the server
 
-  $ echo "[experimental.server]" >> master/.hg/hgrc
-  $ echo "stream-narrow-clones=True" >> master/.hg/hgrc
+  $ echo "[experimental]" >> master/.hg/hgrc
+  $ echo "server.stream-narrow-clones=True" >> master/.hg/hgrc
 
 Cloning a specific file when stream clone is supported