Changing name to OLS in CONTRIBUTING.md

[SaraVilla]

Substituting Mozilla Open Project (no longer relevant I think) for OLS

👍🎉 First of all, thanks for taking the time to contribute! 🎉👍

FOR CONTRIBUTOR

• I have read the CONTRIBUTING.md document

PR Type:

• This PR adds a new blog post
• This PR does something else (explain above)

FOR REVIEWERS

Thanks for taking the time to review! ❤️

Here are the list of things to make sure of:

• The website builds (a check will fail if not)
• All images have been added within the Pull Request and they have Alt text
• If there are paragraphs or text, the key messages are highlighted
• All internal links (within OLS website) use the {% link path_to_file.md %} format
• The preview corresponds to the changes described in the Pull Request
• The code is tidy and passes the linting tests

[yochannah]

🎉 A preview of this PR is available at: https://we-are-ols.org/ols-site-preview/1085/