Remove deprecated global search prometheus metrics

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Remove the following metrics that were marked as deprecated in %17.6 in Add global_search_bulk_cron_embedding_queue_siz... (!171916 - merged) • Madelein van Niekerk • 17.6

• global_search_bulk_cron_queue_size
• global_search_bulk_cron_initial_queue_size
• global_search_awaiting_indexing_queue_size