Merge #13622: Remove mapRequest tracking that just effects Qt display.

Summary:
PR13622 backport https://github.com/bitcoin/bitcoin/pull/13622/files
beef7ec4be725beea870a2da510d2817487601ec Remove useless mapRequest tracking that just effects Qt display. (Matt Corallo)

Pull request description:

I thought we had removed this a long time ago, TBH, its really
confusing feedback to users that we display whether a tx was
broadcast to immediate neighbor nodes, given that has little
indication of whether the tx propagated very far.

Test Plan:
make check
test_bitcoin-qt
Run bitcoin-qt without any peers (connect=0 listen=0) and make a tx; right
click on tx and open full details, observe it doesn't say "has not been
successfully broadcast".

Reviewers: deadalnix, jasonbcox, Fabien, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3477