Modified GR not activated when using ISiTGR

[bastiencarreres]

I was trying to look at density:density power spectrum using transfer_function='boltzmann_isitgr' and I noted that the power spectrum was not changing when using modified gravity parameters.

In boltzmann.get_isitgr_pk_lin at line 274 I noted that GR seems to be enforced by:

 cp.GR = 1  # means GR modified!

According to ISiTGR it should be 0:

integer :: GR = 1 !to use default GR without MG, GR=0 means MG formalism is on

I tested locally, and it solves the issue!