In D8285 we introduced a `showSpinner` prop to the `Avatar` component. In this diff we remove the `LoadingIndicator` from `EditUserAvatar` component and instead pass `showSpinner` down to `Avatar`.
This deduplicates redundant spinner code. Now that we have a "toggleable" spinner in `Avatar`, and components derived from it can use that spinner "for free."
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Depends on D8285