Fix curl example in the `Specifying facet fields` section

[tylere]

Overview

What is the feature/fix?

Fix curl example in the Specifying facet fields section.

What is the Solution?

remove duplicate "/search" from url string.

What areas of the application does this impact?

The public docs.

Checklist

• [ ] I have updated/added unit and integration tests that prove my fix is effective or that my feature works
• [ ] New and existing unit and int tests pass locally and remotely with my changes
• [ ] I have removed unnecessary/dead code and imports in files I have changed
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings