Revert "ci: cache ~/.conan2 in build workflow"

[lia (lia-viam)]

Reverts #84

lost this in my github notifications, but just recording for posterity that caching conan with github actions is basically always an error, for a couple reasons. the simplest one is that this is the exact purpose of the viam artifactory server, so it's an antipattern to be caching on top of a dedicated, purpose-built cache.

the more complex reason is that github actions caching is not fit to purpose for the level of granularity used by conan to cache binary artifacts, and attempts to distinguish github cache artifacts, eg by runner name or platform, will still lead to collisions and races which show up in basically any nontrivial CI matrix.

looking ahead it would be good if we had a canonical "good example" to point people at for how this should be done, which is that CI jobs should use a lockfile to pin dependency versions, and periodically upload dependencies to the viam conan server if they're slowing down CI

[Joseph Borodach (JosephBorodach)]

Sorry I overlooked this. As we discussed offline, once we have that good example if you can point me to it that would be great because we have 3 other camera modules that are caching conan