treediscovery: update test expectation

I'm not sure why this needs an update, but the test passes for me both
pure and non-pure.

Differential Revision: https://phab.mercurial-scm.org/D860

tests/test-treediscovery.t

@@ -552,7 +552,7 b' Both have new stuff in existing named br'
   "GET /?cmd=heads HTTP/1.1" 200 - x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2
   "GET /?cmd=branches HTTP/1.1" 200 - x-hgarg-1:nodes=d8f638ac69e9ae8dea4f09f11d696546a912d961 x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2
   "GET /?cmd=between HTTP/1.1" 200 - x-hgarg-1:pairs=d8f638ac69e9ae8dea4f09f11d696546a912d961-d57206cc072a18317c1e381fb60aa31bd3401785 x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2
-  "GET /?cmd=changegroupsubset HTTP/1.1" 200 - x-hgarg-1:bases=d8f638ac69e9ae8dea4f09f11d696546a912d961&heads=d8f638ac69e9ae8dea4f09f11d696546a912d961 x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2
+  "GET /?cmd=changegroupsubset HTTP/1.1" 200 - x-hgarg-1:bases=d8f638ac69e9ae8dea4f09f11d696546a912d961&heads=d8f638ac69e9ae8dea4f09f11d696546a912d961+2c8d5d5ec612be65cdfdeac78b7662ab1696324a x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2
   "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2
   "GET /?cmd=capabilities HTTP/1.1" 200 -
   "GET /?cmd=heads HTTP/1.1" 200 - x-hgproto-1:0.1 0.2 comp=zlib,none,bzip2