chore: drop old dags

[project-defiant]

Context

This PR drops dags that are no longer used:

• gwas_catalog_processing

Rationale behind the deletion

The processing of GWAS Catalog top hit associations and pics summary statistics is now performed in following dags:

• gwas_catalog_sumstats_pics

• gwas_catalog_top_hits instead of the gwas_catalog_processing.

• gwas_catalog_pipeline

Ragionale behind deletion

This dag was created as a test for running the gwas catalog pipeline for processing data from sumstat harmonisation to susie finemapping. This dag was superseeded by:

• gwas_catalog_sumstat_harmonisation (PR pending action)
• gwas_catalog_sumstats_susie_clumping
• gwas_catalog_simstas_susie_finemapping