Remove duplicated methods in BPINN as it causes methods overwrite

[sathvikbhagavan]

These methods also exist in https://github.com/SciML/NeuralPDE.jl/blob/master/src/PDE_BPINN.jl#L191

Because of this, we get warnings during precompilation.

Precompiling project...
        Info Given NeuralPDE was explicitly requested, output will be shown live 
WARNING: Method definition integratorchoice(Any, Any) in module NeuralPDE at /Users/sathvik/oss/NeuralPDE.jl/src/advancedHMC_MCMC.jl:354 overwritten at /Users/sathvik/oss/NeuralPDE.jl/src/PDE_BPINN.jl:191.
ERROR: Method overwriting is not permitted during Module precompilation. Use `__precompile__(false)` to opt-out of precompilation.
  ? NeuralPDE

cc: @AstitvaAggarwal