undo: remove invalidate_dive_cache() call from make_first_dc()

The make_first_dc() function clones a dive with a certain dive
computer moved to the front. This is used by the
MoveDiveComputerToFront undo command.

make_first_dc() calls invalidate_dive(). However, the undo
command does that by itself on every undo/redo. Thus,
remove the call in make_first_dc().

Aside from consistency, the goal is to move invalidate_dive()
to command/* so that we can be more aggressive about the whole
topic: Store only "const dive *" pointers and thus force any
writing access to explicitly invalidate the dive cache.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/dive.c

@@ -3014,7 +3014,6 @@ struct dive *make_first_dc(const struct dive *d, int dc_number)
 
 	/* make a new unique id, since we still can't handle two equal ids */
 	res->id = dive_getUniqID();
-	invalidate_dive_cache(res);
 
 	if (dc_number == 0)
 		return res;