Auto merge of #66996 - ehuss:update-cargo, r=alexcrichton

Update cargo

11 commits in 750cb1482e4d0e74822cded7ab8b3c677ed8b041..626f0f40efd32e6b3dbade50cd53fdfaa08446ba
2019-11-23 23:06:36 +0000 to 2019-12-03 16:53:04 +0000
- Change some texts to links in README (rust-lang/cargo#7652)
- Update config and environment variable docs. (rust-lang/cargo#7650)
- Stop ignoring .rs.bk files; rustfmt hasn't generated them in years (rust-lang/cargo#7647)
- Various contributing docs updates. (rust-lang/cargo#7642)
- Stabilize profile-overrides. (rust-lang/cargo#7591)
- Update comment about ResolveVersion default version. (rust-lang/cargo#7637)
- Update tests for slight wording change in rustdoc error message. (rust-lang/cargo#7641)
- Remove dep_targets. (rust-lang/cargo#7626)
- vendor: don't use canonical path in .cargo/config (rust-lang/cargo#7629)
- Minor testsuite organization. (rust-lang/cargo#7628)
- Remove failing plugin tests. (rust-lang/cargo#7630)