reftable/record: drop unused print function pointer

In 42c424d69d (t/helper: inline printing of reftable records,
2024-08-22) we stopped using the `print` function of the reftable record
vtable and instead moved its implementation into the single user of it.
We didn't remove the function itself from the vtable though. Drop it.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reftable/record.h

@@ -73,9 +73,6 @@ struct reftable_record_vtable {
 	 * the same type.
 	 */
 	int (*cmp)(const void *a, const void *b);
-
-	/* Print on stdout, for debugging. */
-	void (*print)(const void *rec, int hash_size);
 };
 
 /* returns true for recognized block types. Block start with the block type. */