fix hot tags tests failing based on time of the month

[amirRamirfatahi]

Fixes #273

Pre-submission Checklist

For tests to work you need a working neo4j and redis instance with the example dataset in docker/db-graph

• Testing: Implement and pass new tests for the new features/fixes, cargo test.
• Performance: Ensure new code has relevant performance benchmarks, cargo bench

[tipogi]

In hot-tags.cypher, the day and month params are unused. Looks good that implementation 🚀

[SHAcollision]

Looks good to me, just remove the unused code @tipogi pointed out and ready to merge.