Remove misleading gitlab-foss reference in README.md
After the single repo migration from Gitlab EE and CE, all FOSS & enterprise development takes place in one repo.
This MR removes the misleading reference and link to the previous read-only Gitlab Community Edition project in the Gitlab Readme file.
- Having a link to the obsolete, read-only gitlab-foss repo right at the top is misleading for users
- The word 'FOSS' misleads people to believe the current repo isn't free and open source software.
This issue was resolved via this MR.