Fixing docstring for setDimension

[john-science]

Description

This was a documentation upgrade suggested by @jasonbmeng in Issue #1011

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Checklist

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

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

• The release notes (location doc/release/0.X.rst) are up-to-date with any bug fixes or new features.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in setup.py.

[keckler]

I think this is a good change.

I would also propose that the way this method is written is kinda goofy. The logic makes it so we always calculate expansionFactor, whether or not it is used. This is (1) wasteful and (2) restricts us to only setting dimensions on components with materials that have the thermal expansion parameter defined.

Not super related to this PR, but just noticed it in the process of reviewing.