After Haystack 2.21 release: remove `QueryExpander`, `MultiQueryTextRetriever` and `MultiQueryEmbeddingRetriever`

[anakin87]

Components have been migrated to Haystack in deepset-ai/haystack#10126.
After 2.21 release, we should remove them from experimental.

Steps for Moving an Experiment to Haystack Core or Integrations

• Make sure the latest Haystack release or an integration release contains the merged experiment
• Close discussion in haystack-experimental with move information
• Remove pydocs
• Move experiment from active experiments in the catalog in haystack-experimental README.md to adopted experiments
• Remove dependencies needed for the experiment from pyproject.toml

[davidsbatista]

I can take over this one.