Remove the last comma when making buildH json file

[patrickfuchs]

The function gen_buildH_json_lipid() in autoLipMap_lib.py, the last line shouldn't have a comma. Currently, the function generates this:

[...]
    "C29": ["CH3", "C27", "C26"],
    "C28": ["CH3", "C27", "C26"],
}

whereas it should be:

[...]
    "C29": ["CH3", "C27", "C26"],
    "C28": ["CH3", "C27", "C26"]
}