BUG - Contributors check runs till rate limit is exhausted

[daniel-grund]

Describe the bug
Running a scorecard check for contributors against https://github.com/DefinitelyTyped/DefinitelyTyped consumes the full github API ratelimit of 5000 without returning a response.

Reproduction steps
Steps to reproduce the behavior:

1. Run the command line scorecard check with ./scorecard --repo=github.com/DefinitelyTyped/DefinitelyTyped --checks Contributors
2. Observe your rate limit on the github API using https://api.github.com/rate_limit
3. The rate limit is being used until nothing is left. The command line just shows "Starting [Contributors]"

Expected behavior
The contributors check shall be performed on the mentioned repository

Additional context
https://github.com/DefinitelyTyped/DefinitelyTyped has a pretty huge CODEOWNERS file which might be part of the issue.

[spencerschrock]

The Contributors check has always been API quota heavy. Repositories with a large amount of contributors never fully consumed API quota because GitHub's API for listing contributors would error in repos with too many contributors.

pretty huge CODEOWNERS file which might be part of the issue

But as of #4611 we also started making API calls for users in a CODEOWNERS file, which is the issue here as there look to be more than 5k codeowners. We should add some limit on number of contributors we parse