merge axes capability mix up link for tooltips

[lee1043]

See the linked path at the bottom of above image, which is shown such as:
"... /v20200602/zg-500_global//zg-500_global_cmip6_historical_ACCESS-CM2_djf_.png"

which supposed to be:
"... /v20200602/zg-500/global/zg-500_cmip6_historical_ACCESS-CM2_djf_global.png"

merge = [["model"], ["variable", "region"]]

https://github.com/PCMDI/PCMDI_Simulation_Summaries/blob/927296466f74faad04b32483372aa0906e408b85/graphic/mean_climate/click/params_modal_meanclimate.py.in#L97

cell_tooltips_images_template = os.path.join(
        "../../../../../../../..",
        "graphics", "mean_climate", mip, exp, "clim", graphic_ver, "%(variable)", "%(region)",
        "%(variable)_"+mip+"_"+exp+"_%(model)_%(season)_%(region).png")

https://github.com/PCMDI/PCMDI_Simulation_Summaries/blob/927296466f74faad04b32483372aa0906e408b85/graphic/mean_climate/click/params_modal_meanclimate.py.in#L194

[lee1043]

Influenced by names_update