footnote font size down one to xs

[sforschen]

Please always provide the GitHub issue(s) your PR is for, as well as test URLs where your change can be observed (before and after):

Fix #170

Test URLs:

• Before: https://main--elixirsolutions--hlxsites.hlx.live/
• After: https://footnote-downsize-font--elixirsolutions--hlxsites.hlx.live/

[aem-code-sync[bot]]

Hello, I'm Franklin Bot and I will run some test suites that validate the page speed. In case there are problems, just click the checkbox below to rerun the respective action.

• [ ] Re-run PSI Checks

[aem-code-sync[bot]]

Page	Scores	Audits	Google
/

[sforschen]

This is specifically used in the blogs, the bottom of any page.

[sforschen]

@janefrommaine I realized I didn't switch back to main for subsequent changes after this one so if we merge oldest to new it will be ok.