covariance_matrix_plots runcard fails with 5bar pt. prescription

Created by: andreab1997

Running the covariance_matrix_plots runcard with the 5bar point prescription (as in covariance_matrix_plots_5barpt_reduced.txt) results in: Choice of input theories does not correspond to a valid prescription for theory covariance matrix calculation This could be linked to the absence of the flag fivetheories in https://github.com/NNPDF/nnpdf/blob/9840fc69dfcbcf25ebb30236916c4f1fc65a1785/validphys2/src/validphys/config.py#L1515