fab9b60 doc: Remove outdated minrelaytxfee comment (MarcoFalke)
Tree-SHA512: e36c5a554a9773f034c2d358c52a772688009a5a71dfd3f664d9b5566c98378f44ef7c6dc0902b42d69ab5fd54b60d4850a2903823d0b2309c7ae063d1923f7f
Backport of PR10626
https://github.com/bitcoin/bitcoin/pull/10626/
contrib/devtools/check-doc.py was used for travis, so those changes have not been included.