update ahrefs job (#909)

The https://ahrefs.com/jobs/ocaml-developer position is ever green, publication date is not relevant

Author: Khady

data/jobs.yml

@@ -13,7 +13,6 @@ jobs:
   - title: OCaml Developer
     link: https://ahrefs.com/jobs/ocaml-developer
     location: Remote
-    publication_date: 2020-09-22
     company: Ahrefs
     company_logo: /logos/ahrefs.svg
   - title: OCaml Developer