Replace legacy TransformersSimilarityRanker with SentenceTransformersSimilarityRanker

[julian-risch]

haystack.components.rankers.transformers_similarity:TransformersSimilarityRanker is considered legacy and will no longer receive updates. It may be deprecated in a future release, with removal following after a deprecation period. We should use SentenceTransformersSimilarityRanker instead, which provides the same functionality along with additional features.

[anakin87]

Done in #460