test: reduce the stress in the manyrma2 test

[hzhou]

Pull Request Description

The manyrma2 tests are often falsely triggered due to performance issue, especially for some configuration such as the asan tests. Lower the MAX_RUNS from 8 to 2 since our CI tests should focus on correctness. We'll focus on catching performance CI in the bench tests.

[skip warnings]

Author Checklist

• [x] Provide Description Particularly focus on why, not what. Reference background, issues, test failures, xfail entries, etc.
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• [ ] Passes All Tests Whitespace checker. Warnings test. Additional tests via comments.
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[hzhou]

test:mpich/ch4/ofi

[raffenet]

The performance tests are not stress tests, so they will not make up for the reduced stress in this test. I don't think this is the right change.