exchange: stop advertising rev-branch-cache bundle capability

Since Mercurial 5.7, the corresponding bundle part is ignored as
redundant. Stop advertising it so that peers don't have to spend time
creating or transfering it.

Differential Revision: https://phab.mercurial-scm.org/D10114
13 jobs for topic/default/rbc-deprecation in 26 minutes and 8 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Tests
passed #172880
checks-py2

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checks-py3

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rust-cargo-test-py2

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rust-cargo-test-py3

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test-py2

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test-py2-chg

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test-py2-pure

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test-py2-rust

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test-py3

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test-py3-chg

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passed #172887
test-py3-pure

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passed #172889
test-py3-rust

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  Phabricator
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phabricator-refresh

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