badges: Raise limits for PRs merged with 0 retest

[brianmcarey]

What this PR does / why we need it:

The merged PRs with 0 retest has been regularly over 50% of total merged PRs. This currently marks the badge as green.

Lets raise the bar for a green badge to 75% and over. While below 50% will now mark the badge as red.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

/cc @dhiller @xpivarc

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• Design: A design document was considered and is present (link) or not required
• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
• Community: Announcement to kubevirt-dev was considered

Release note:

[dhiller]

The merged PRs with 0 retest has been regularly over 50% of total merged PRs. This currently marks the badge as green.

👍 thanks @brianmcarey !

[dhiller]

/approve

[xpivarc]

What a milestone btw 🍾

[brianmcarey]

What a milestone btw 🍾

Yes i thought it was a nice little change to make.

There are a couple of other limits for the rest of the badges that could probably be updated. Will take a look.