Deprecate react-unit-test-utils 8/15

[diana-villalvazo-wgu]

Remove use of 'shallow' (react-unit-test-utils) in following files:

• src/containers/CoursesPanel/index.test.jsx
• src/containers/Dashboard/DashboardLayout.test.jsx
• src/containers/Dashboard/index.test.jsx
• src/containers/Dashboard/LoadingView.test.jsx
• src/containers/EmailSettingsModal/index.test.jsx

[diana-villalvazo-wgu]

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