Auto merge of #5215 - alexcrichton:update-version, r=matklad

Don't require `cargo update` when bumping versions

One historical annoyance I've always had with Cargo that I've found surprising
is that in some situations when you bump version numbers you'll have to end up
running `cargo update` later on to get everything to build. You get pretty wonky
error messages in this case as well saying a package doesn't exist when it
clearly does at a particular location!

I've had difficulty historically nailing down a test case for this but it looks
like we ironically already had one in our test suite and I also jury-rigged up
one from a case I ran into in the wild today.