Reduce the pytest job parallelism from 10 to 6

[kptkin]

Description

What does the PR do?

This PR reduces the pytest parallelism from 10 to 6 in the hopes to make CircleCi happier

Testing

How was this PR tested?

Hopefully over time the flake should be reduced

[codecov]

Codecov Report

Merging #4085 (63c7218) into master (d687bf3) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head 63c7218 differs from pull request most recent head c64b5ba. Consider uploading reports for the commit c64b5ba to get more accurate results

@@            Coverage Diff             @@
##           master    #4085      +/-   ##
==========================================
+ Coverage   82.74%   82.75%   +0.01%     
==========================================
  Files         255      255              
  Lines       32266    32266              
==========================================
+ Hits        26699    26703       +4     
+ Misses       5567     5563       -4     

Flag	Coverage Δ
functest	54.93% <ø> (+<0.01%)	⬆️
unittest	73.45% <ø> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
wandb/sdk/lib/sock_client.py	89.92% <0.00%> (-1.44%)	⬇️
wandb/sdk/service/server_sock.py	91.87% <0.00%> (-1.02%)	⬇️
wandb/sdk/launch/runner/local_container.py	79.80% <0.00%> (-0.97%)	⬇️
wandb/sdk/internal/internal_api.py	86.39% <0.00%> (-0.52%)	⬇️
wandb/sdk/wandb_setup.py	88.50% <0.00%> (-0.50%)	⬇️
wandb/sdk/lib/git.py	79.01% <0.00%> (ø)
wandb/sdk/wandb_run.py	91.26% <0.00%> (+0.24%)	⬆️
wandb/sdk/launch/agent/agent.py	92.95% <0.00%> (+0.70%)	⬆️
wandb/integration/tensorboard/monkeypatch.py	92.59% <0.00%> (+2.46%)	⬆️
wandb/sdk/internal/meta.py	90.79% <0.00%> (+3.06%)	⬆️
... and 1 more