Update docstrings for bitwise functions

[antonwolfy]

The PR updates docstrings for bitwise functions to have a blank line prior Default value.

• Have you provided a meaningful PR description?
• Have you added a test, reproducer or referred to an issue with a reproducer?
• Have you tested your changes locally for CPU and GPU devices?
• Have you made sure that new changes do not introduce compiler warnings?
• Have you checked performance impact of proposed changes?
• Have you added documentation for your changes, if necessary?
• Have you added your changes to the changelog?

[github-actions]

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

[coveralls]

coverage: 71.929%. remained the same
when pulling 916ef9e on update-bitwise-docstrings
into 2700d92 on master.

[github-actions]

Array API standard conformance tests for dpnp=0.18.0dev0=py312he4f9c94_21 ran successfully.
Passed: 1006
Failed: 0
Skipped: 17