Fixing hex assembly rotation docs

[drewj-tp]

What is the change?

Caught some typos and errors in docs that were previously introduced by me that made the docs render poorly.

Why is the change being made?

Docs should be buildable and look nice.

Fix bad doc directive in block parameters

Resolves the following error from doc
builds

/home/runner/work/armi/armi/doc/user/spatial_block_parameters.rst:126:
ERROR: Unknown directive type "seelso".

.. seelso::

    The :ref:`LWR tutorial <walkthrough-lwr>` contains additional
examples for working with sub-block grids.

Move discussion on getOptimalAssemblyRotation out of Notes section

This doesn't seem to render well inside a note box. Not sure why it is not a unique section but its own admonition box

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify any new/changed code.

• The code style follows good practices.
• The commit message(s) follow good practices.

• The release notes have been updated if necessary.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in pyproject.toml.