Jobs section for profile.wordpress.org: only ask for month and year for roles

Currently, we ask for days rather than just month and year for roles, which is a high bar!

<img width="849" height="272" alt="Image" src="https://github.com/user-attachments/assets/9ae58dd1-c103-4da9-994e-dde6e0d88271" />

LinkedIn only asks for month and year:

<img width="605" height="196" alt="Image" src="https://github.com/user-attachments/assets/005a1da0-9f4a-4e89-901b-adea9bba70fe" />

