Change access setup for .eclipsefdn repo

The permissions that should be given to the .eclipsefdn repo:

• security team: write permission
• releng team: write permission
• project lead team: triage permission
• committers team: read permission

Reasoning: the project leads should be able to close PRs they find inappropriate.

The read permissions for the committers team is actually useless as it is a public repo now and everybody can clone the repo and create issues and PRs. This was an artifact from the time when the repo was supposed to be private and also led to some confusion by myself. To add the project leads makes sense imho, we already received feedback from projects that they are concerned with PRs opened from anyone, so to give them at least some power to close PRs that are not valid.