[Libomptarget] Remove undefined 'omp_get_interop_rc_desc' symbol from exports list

Summary:
A recent patch made undefined symbols in version scripts cause errors by
default. The `omp_get_interop_rc_desc` function is declared but not
defined, so it is undefined in the final link unit. This patch removes
it from the exports list, it should be added back in when actually
defined and used.