Typo in docs: missing word "default" in Butcher.rst

[cjvogl]

Found a missing word in the docs for the Yoshida Butcher Table constant description.

• Please target the develop branch not main.
• Review our Contributing Guide, and ensure that you sign your last commit (at minimum) as per the guide.
• Provide a concise description of what your pull request does, and why it is needed/benefical.
• Add a note about your change to the CHANGELOG.md and docs/shared/RecentChanges.rst files. Notice that the former is a markdown file and the latter is reStructuredText, so the formatting is slightly different.
• After your PR is opened, ensure that all of the tests are passing (a SUNDIALS developer will have to allow the testing to run).

[cjvogl]

@gardner48 , apologies that I keep forgetting to branch off develop instead of main