tests: do not create repos inside repos in test-rename-merge1.t

This is no actual problem, but I when adding more tests to this file,
the directory structure would become t/repo2089/repoXXXX/repoYYYY/...

tests/test-rename-merge1.t

@@ -123,6 +123,8 b' Check for issue2642'
   $ cat f2
   c0
 
+  $ cd ..
+
 Check for issue2089
 
   $ hg init repo2089
@@ -152,3 +154,5 b' Check for issue2089'
 
   $ cat f2
   c2
+
+  $ cd ..