mc2hessian action doesn't write the correct error type

Created by: Zaharid

The following runcard

pdf: NNPDF31_nnlo_as_0118_1000
Q: 100
Neig: 25

mc2hname: "nnpdf_31_nnlo_hessian_25"

installgrid: True

actions_:
    - mc2hessian

should write ErrorType: symmhessian in the info file.

Instead if I look at it

$ 
cat nnpdf_31_nnlo_hessian_25.info  | grep ErrorType
ErrorType: replicas