Remove reference tags from section headings

Airflow test run results:

snapshot = '2024-02-19'
prod = spark.read.table('analytics_platform_eng.image_suggestions_suggestions').where(f'snapshot="{snapshot}" and section_index is not null')
dev = spark.read.table('slis_no_ref.image_suggestions_suggestions').where(f'snapshot="{snapshot}" and section_index is not null')
prod.count(), dev.count()
(3417560, 3419662)

prod.where("section_heading like '%<ref%'").count()
742
dev.where("section_heading like '%<ref%'").count()
0

Bug: T341113