Rollup merge of #138053 - Kobzol:more-try-jobs, r=marcoieni

Increase the max. custom try jobs requested to `20`

Requested [here](https://rust-lang.zulipchat.com/#narrow/channel/242791-t-infra/topic/Increase.20try-job.20limit).

r? ````@marcoieni````

Author: compiler-errors