Enable filtering with BM25 search in Weaviate now that it is supported with v1.18.0

[zoltan-fedor]

Is your feature request related to a problem? Please describe.
Filtering with BM25 search was not supported prior to Weaviate v1.18.0, but with this version now it is supported in Weaviate, so we need to support it from Haystack when the Weaviate document store is used.

Describe the solution you'd like
I have made comments in the code before regarding the places where changes need to be made once this becomes available in Weaviate, so now we just need to uncomment those to make this work.

Describe alternatives you've considered
N/A

Additional context
I will submit a PR for this.