jit: remove some unused fields from recording::union_ (PR jit/81672)

jit: remove some unused fields from recording::union_ (PR jit/81672)

gcc::jit::recording::union_ has some stray fields, which
are duplicates of those in the compound_type base class.

It looks like these have been present since the initial merger of the jit
branch to trunk (r217374), where it had three duplicate fields:

 location *m_loc;
 string *m_name;
 fields *m_fields;

I removed the duplicate field "m_fields" in r219564 but missed the other
two.

This patch removes them.

gcc/jit/ChangeLog:
	PR jit/81672
	* jit-recording.h (gcc::jit::recording::union_): Remove fields
	"m_loc" and "m_name".

From-SVN: r257066