Add support for python-box 7

[ericpre]

A change in python-box 7 https://github.com/cdgriffith/Box/issues/192 broke the the CEOS Panta Rhei (PRZ) code because of the use of period containing keys.

Progress of the PR

• [x] Where necessary, use DTBox(dict, box_dots=False, default_box=True) to support period containing keys,
• [x] unpin python-box,
• [x] update docstring (if appropriate),
• [n/a] update user guide (if appropriate),
• [x] add a changelog entry in the upcoming_changes folder (see upcoming_changes/README.rst),
• [x] Check formatting of the changelog entry (and eventual user guide changes) in the docs/readthedocs.org:rosettasciio build of this PR (link in github checks)
• [n/a] add tests,
• [x] ready for review.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.54839% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 86.36%. Comparing base (a7327e4) to head (8177f20).

Files	Patch %	Lines
rsciio/pantarhei/_api.py	93.54%	0 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #263 +/- ## ========================================== - Coverage 86.37% 86.36% -0.01% ========================================== Files 83 83 Lines 10653 10655 +2 Branches 2322 2322 ========================================== + Hits 9201 9202 +1 - Misses 935 936 +1 Partials 517 517 ```

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[ericpre]

Failures are related to https://github.com/hyperspy/rosettasciio/pull/262.