Tune tolerance in matvec test

[antonwolfy]

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/pull/2912/index.html

[coveralls]

coverage: 78.444%. remained the same — relax-tol-in-matvec-test into master

[github-actions]

Array API standard conformance tests for dpnp=0.21.0dev0=py313h509198e_17 ran successfully.
Passed: 1356
Failed: 4
Skipped: 16