preinstalled boost requires update to 1.86.0

[evoskuil]

This is a consequence of me upping boost from 1.78 to 1.86. Boost 1.87 (latest) has a single unresolved external in the NuGet .lib, so went with 1.86. All builds appear to be clean, though I won't know for sure until I start merging them up. I've left these three (presents builds) broken because they compile in the standard cmake builds.

CMake Error at /usr/local/share/cmake-3.31/Modules/FindPackageHandleStandardArgs.cmake:233 (message):
  Could NOT find Boost: Found unsuitable version "1.78.0", but required is at
  least "1.86.0"...

https://github.com/libbitcoin/libbitcoin-system/actions/runs/15239758487/job/42858355628#step:10:498

[pmienk]

Resolved by subsequent checkin to build.