Remove private competitions and competition participants counters from home page

Total competitions counter is not relevant because it counts many templates and testing competitions. Very few private competitions are real benchmarks. Competition participants is basically the number of users.

Before:

After:

Checklist

• Code review by me
• Hand tested by me
• I'm proud of my work
• Code review by reviewer
• Hand tested by reviewer
• CircleCi tests are passing
• Ready to merge