chore: tag 0.5.6

[jrconlin]

Features

• More purge_ttl features (feat: More purge_ttl features #776) (59aa28a4, closes #735, #743)

Bug Fixes

• remove ubuntu target for grpcio (bug: remove ubuntu target for grpcio  #775) (7d1061f7, closes #774)
• Return WeaveError::OverQuota for over quota responses (bug: Return WeaveError::OverQuota for over quota responses #773) (38cd5ddd, closes #769)
• ensure an X-Last-Modified for /info/configuration (fix: ensure an X-Last-Modified for /info/configuration #761) (36533f85, closes #759)

[jrconlin]

It's sad that this tag will probably never see production.

It has the debug_client option, is built off of the 0.5 base (which is showing odd hiccups on stage), and there's a 0.4 that's getting submarined in that will most likely be reverted shortly after.

Closing this for now.