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

• src/editors/containers/VideoEditor/components/VideoSettingsModal/components/VideoSourceWidget/index.test.jsx
• src/editors/containers/ProblemEditor/components/EditProblemView/SettingsWidget/settingsComponents/GeneralFeedback/index.test.jsx
• src/editors/containers/ProblemEditor/components/EditProblemView/ExplanationWidget/index.test.jsx
• src/editors/containers/VideoEditor/components/VideoSettingsModal/components/LicenseWidget/index.test.jsx
• src/editors/containers/VideoEditor/components/VideoSettingsModal/components/ThumbnailWidget/index.test.jsx
• src/plugin-slots/AdditionalCourseContentPluginSlot/index.test.jsx