Fix: Free table_positions in sz_sequence_intersect_serial and _ice

Both intersect implementations allocated the linear-probing hash table
via `alloc->allocate(...)` at function entry but never released it on
the success path, leaking `hash_table_slots * (sizeof(sz_size_t) +
sizeof(sz_u64_t))` bytes per call. LeakSanitizer flagged this as 6
direct leaks (~50 KiB total) in `test_intersecting_algorithms`. Add the
missing `alloc->free(...)` before the final `return sz_success_k;` in
each function. The `sz_bad_alloc_k` early return needs no free since
the allocation itself failed.

Author: ashvardanian

include/stringzilla/intersect.h

@@ -339,6 +339,7 @@ SZ_PUBLIC sz_status_t sz_sequence_intersect_serial(
         }
     }
 
+    alloc->free(table_positions, hash_table_slots * bytes_per_entry, alloc);
     *intersection_count_ptr = intersection_count;
     return sz_success_k;
 }
@@ -721,6 +722,7 @@ SZ_PUBLIC sz_status_t sz_sequence_intersect_ice(
     }
 
     // Finalize
+    alloc->free(table_positions, hash_table_slots * bytes_per_entry, alloc);
     *intersection_count_ptr = intersection_count;
     return sz_success_k;
 }