More docs fixes

[kurtmckee]

Pull Request check-list

Please make sure to review and check all of these items:

• Do tests and lints pass with this change?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?
• Was the change added to CHANGES file?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Description of change

This PR resolves three classes of warnings and errors that Sphinx reports when building the documentation (recent example; click the python -m sphinx accordion to see the details):

• "Unexpected indentation"
• "Unexpected unindent"
• "more than one target for cross-reference 'Redis'"

[kurtmckee]

Friendly ping.

This resolves more classes of build warnings that are thrown during documentation builds (examples of remaining warnings that I'd like to resolve after this PR merges). 😀

[kurtmckee]

Hello @gerzse and @vladvildanov! Please review this PR when you can. It addresses three categories of documentation build warnings.

If this merges, there will only be one documentation warning category left: "reference target not found".

docstring of redis.commands.core.BasicKeyCommands.getex:: WARNING: py:class reference target not found: datetime.datetime
docstring of redis.commands.core.HashCommands.hexpire:1: WARNING: py:class reference target not found: datetime.timedelta
docstring of redis.commands.core.HashCommands.hexpire:1: WARNING: py:class reference target not found: Returns a list which contains for each field in the request

[vladvildanov]

@kurtmckee Thank you for your contribution!