get rid of unnecessary template in the backend of dot functions

[vtavana]

In this PR, unnecessary template in the backend of dot functions is removed.

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[github-actions]

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

[coveralls]

coverage: 72.168% (-0.003%) from 72.171%
when pulling 912499a on simplify-dot
into 008dc96 on master.

[github-actions]

Array API standard conformance tests for dpnp=0.18.0dev0=py312he4f9c94_48 ran successfully.
Passed: 1197
Failed: 0
Skipped: 14

[antonwolfy]

Thank you @vtavana for the code cleanup. LGTM!