remove @views

[norci]

ref: https://docs.julialang.org/en/v1/manual/performance-tips/#Copying-data-is-not-always-bad

[findmyway]

Well, select_last_dim is provided as a general function to select slices in the last dimension, an enhancement to Base.selectdim. So when performance is the main issue, it's the user's responsibility to convert it into an Array explicitly.

[findmyway]

By the way, the potential performance issue of @views will be addressed in JuliaReinforcementLearning/ReinforcementLearningCore.jl#169 .