fix(ci): remove redundant --concurrency test run in CI

[dorimedini-starkware]

This change is 

[noaov1]

As it will anyway be with concurrency because of the native blockifier?
We don't get to run cargo test blockifier without neededing to test native blockifier as well?
Will we run the blockifier without concurrency?

Reviewed 1 of 2 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @dorimedini-starkware)

[dorimedini-starkware]

the only way to test blockifier without concurrency is if it's tested without the NB, i.e. cargo test -p blockifier.
this is done in the blockifier_ci workflow, so no need for it in the main CI.
run tests will never test the blockifier without concurrency because NB depends on B

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @dorimedini-starkware)