Replace remaining Styra references

[anderseknert]

With the exception of links to the Styra blog, we should replace links pointing to Styra resources with the equivalent OPA doc pointer. I noticed today as I clicked to view "Examples" after hovering a contains keyword that I got to sent to the Styra docs on the topic. These docs are in OPA now though, and we should point to them instead. I am however not 100% sure how it's all wired together, so would be helpful to pair up on this with someone who knows.

See:

• https://github.com/open-policy-agent/regal/blob/main/internal/lsp/examples/examples.go#L16
• https://github.com/open-policy-agent/regal/blob/main/build/workflows/update_example_index.rego#L61

I have replaced other references in #1904