tests: make the commands.resolve.confirm tests not pollute the test-wide hgrc

I want to add tests after these tests that create a new repo and use it, and was
confused for a bit as to why they were seeing different behavior than I
expected.

Differential Revision: https://phab.mercurial-scm.org/D5242

tests/test-resolve.t

@@ -525,7 +525,7 b' Test when commands.resolve.confirm confi'
 
 Test when config option is set:
 ==============================
-  $ cat >> $HGRCPATH << EOF
+  $ cat >> .hg/hgrc << EOF
   > [ui]
   > interactive = True
   > [commands]