[anti-censorship-team] goptlib v1.6.0

I tagged v1.6.0 of goptlib. It has a bug fix (panic in DialOr) and a corrected test case.

https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/goptl...

== v1.6.0

Fixed a type assertion panic in DialOr that occurred when the network dial failed. Patch by Rob Jansen. https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/goptl...

Enhanced the TestGetServerBindaddrs test to compare not only MethodName and Addr, but also Options, and fixed a test case that expected the wrong Options. Patch by Jack Wampler. https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/goptl...