Upgrade to emotion v10

Summary: React 16 is not compatible with react-emotion 9 (it prints warnings, see also https://github.com/emotion-js/emotion/issues/644). So we should upgrade to 10.

Reviewed By: mweststrate

Differential Revision: D18905889

fbshipit-source-id: c00d2dbbadb1c08544632cb9bfcd63f2b1818a25

src/plugins/sandbox/index.tsx

@@ -45,7 +45,7 @@ export default class SandboxView extends FlipperPlugin<
     showFeedback: false,
   };
 
-  static TextInput = styled('input')({
+  static TextInput = styled.input({
     border: `1px solid ${colors.light10}`,
     fontSize: '1em',
     padding: '0 5px',
@@ -55,7 +55,7 @@ export default class SandboxView extends FlipperPlugin<
     flexGrow: 1,
   });
 
-  static FeedbackMessage = styled('span')({
+  static FeedbackMessage = styled.span({
     fontSize: '1.2em',
     paddingTop: '10px',
     color: 'green',