revert: remove unused debug code in the test file

I left a test environment variable in a previous commit and it is doing nothing
useful. This patch removes it.

tests/test-revert-interactive.t

@@ -292,7 +292,7 b' 3) Do another commit on top'
   $ hg st
 
 4) Use interactive revert to recover f and change it on the fly
-  $ HGEDITOR="\"sh\" \"${TESTTMP}/editor.sh\"" PRINTHUNK="YES" hg revert -i -r ".^^"  <<EOF
+  $ HGEDITOR="\"sh\" \"${TESTTMP}/editor.sh\"" hg revert -i -r ".^^"  <<EOF
   > y
   > e
   > EOF