Remove unused function G1SATBCardTableLoggingModRefBS::write_ref_field_static()

The function G1SATBCardTableLoggingModRefBS::write_ref_field_static() is currently never used. All post-barrier calls seems to be made directly to G1SATBCardTableLoggingModRefBS::write_ref_field_work(), which does the same thing except for filtering out inter-region references.

Either the _static function should be removed completely, or calls to the _work function should be changed to instead be calls to the _static version (but I'm not sure if this has some unexpected side-effect).