Move MOM_generic_tracer with no changes (#22)

* Move MOM_generic_tracer with no changes

Renames src/tracer/MOM_generic_tracer.F90
to config_src/external/GFDL_ocean_BGC/MOM_generic_tracer.F90

* Remove MOM_generic_tracer

Git rm MOM_generic_tracer.F90

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Co-authored-by: Theresa Morrison <Theresa.Morrison@gaea68.ncrc.gov>

Author: 2 people