[avalanche][trivial] Fix an obsolete comment in net processing
[avalanche][trivial] Fix an obsolete comment in net processing

Summary: addProof is now called registerProof.

Test Plan:
  NOP()

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D10754

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