Switch to OLS 4

[ljwh2]

OLS3 will be switched off in October 2023. All parts of the GWAS Catalog infrastructure that use OLS must be switched over to OLS4.

The first step is to identify all parts of the infrastructure that use OLS.

So far I know of:

• [ ] slim solr - driving the homepage search bar
• [ ] fat solr
• [x] links out from the trait page to OLS