internal-doc: document the 'phases' parameters to 'getbundle' stable

internal-doc: document the 'phases' parameters to 'getbundle'

The getbundle wireprotocol method has some extended documentation. We update it
with the next parameters introduced for binary phases.

--- a/mercurial/help/internals/wireprotocol.txt	Sat Oct 28 00:00:05 2017 -0400
+++ b/mercurial/help/internals/wireprotocol.txt	Fri Oct 27 21:35:34 2017 +0200
@@ -731,6 +731,8 @@
 cbattempted
    Boolean indicating whether the client attempted to use the *clone bundles*
    feature before performing this request.
+phases
+   Boolean indicating whether phases data is requested.
 
 The return type on success is a ``stream`` where the value is bundle.
 On the HTTP transport, the response is zlib compressed.