Fix Bug in `aero_model_emissions::calc_org_matter_seasalt()`

[mjs271]

There is a known bug in the function aero_model_emissions::calc_org_matter_seasalt() located here.

Based on the inline comments and discussion with @singhbalwinder, @mingxuanwupnnl, and the original author, it appears that

alpha_help(:) = sum(theta, dim=2)

should be replaced by

alpha_help(:) = sum(theta_help, dim=2)

Note: Fixing this bug will be held until validation against the fortran MAM4 is complete.