Fix Be orbital optimization test

[markdewing]

Some fixes for #4619:

1. Check correct series number.
2. Skip test for mixed precision builds.

What type(s) of changes does this code introduce?

Delete the items that do not apply

• Bugfix
• Testing changes (e.g. new unit/integration/performance tests)

Does this introduce a breaking change?

• No

What systems has this change been tested on?

desktop

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• Yes. This PR is up to date with current the current state of 'develop'
• N/A. Code added or changed in the PR has been clang-formatted
• Yes. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• N/A. Documentation has been added (if appropriate)

[markdewing]

Test this please