Suppress a flaky internal mypy error appearing randomly when executing make lint.

[fressi-elastic]

Fixes Rally issue #1918.

[gbanasiak]

@fressi-elastic I've removed \@sakurai-youhei, no need to engage him. Better to use @elastic/es-perf unless someone has specific context. The scope of the change is bigger than the title, is that expected?

[fressi-elastic]

@fressi-elastic I've removed \@sakurai-youhei, no need to engage him. Better to use @elastic/es-perf unless someone has specific context. The scope of the change is bigger than the title, is that expected?

No the scope is the one in the title. I included other changes by mistake. I am sorry for it. I am going to remove unrelated changes from this one.

[gbanasiak]

I assume this makes mypy check slower under pre-commit, but correctness is more important than speed. We can revisit if this becomes too slow for us for some reason.

[fressi-elastic]

The speed difference are irrelevants with my M4 14 cores MacBook. I also guess that the reason I see so many errors is because I was working with so many fast cores. With less and slower cores probably race conditions are harder to spot. Anyway considering the correctness and reliability of tests is much more important than speed I agree that we should wait the bug is fixed on mypy side before restoring this configuration as it was before.