Refactor unit tests using enzyme render to avoid EUI upgrade mentions

[justinkambic]

Today, when the EUI team upgrades to a new version we are frequently mentioned for CODEOWNER review when snapshots change. These almost always change because the EUI team adds some new class or attribute to the components they maintain, which then break our snaps.

Given that they only merge breaking changes for majors, we can reduce a marginal amount of noise for ourselves and work for the EUI maintainers by refactoring any test that breaks when an upgrade happens. In the example PR linked above, two of our test suites required such revision.