Remove `boost` wrapper port, it keeps breaking different dependents of Boost

[barracuda156]

The wrapper port serves no good purpose, its only function is breaking various consumers of Boost libs.

Just another example: ​https://github.com/NickvisionApps/libnick/issues/50

These errors never show up on CI or buildbots, for obvious reasons, but the current set-up is wrong. It wastes time on debugging and then forces to add per-port hacks via conflicts_build.