Move odata loading message and spinner styles to the right place

[ktuite]

Closes getodk/central#603 and closes getodk/central#526

CSS to style the spinner and message text for the OdataLoadingMessage component is now in the right place. This shows up on the Entities page and Submissions page.

What has been done to verify that this works as intended?

Why is this the best possible solution? Were any other approaches considered?

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Does this change require updates to user documentation? If so, please file an issue here and include the link below.

Before submitting this PR, please make sure you have:

• run npm run test and npm run lint and confirmed all checks still pass OR confirm CircleCI build passes
• verified that any code or assets from external sources are properly credited in comments or that everything is internally sourced