Remove un-needed "il1g" variable from ZM schemes.

Currently the `zm_conv_convtran_run` and `zm_conv_momtran_run` schemes have an "il1g" input variable which has a standard name of `index_of_first_column_of_gathered_deep_convection_arrays`.

However, in CAM and CAM-SIMA this variable appears to be hardcoded to one. Thus it would likely clean-up the code if this variable was removed from the relevant subroutine arguments and instead just made a local variable (or all of the relevant uses of the variable were simply replaced with `1`).

Note that once this issue has been resolved the "il1g" variable can also be removed from the CAM-SIMA registry as well.