Upgrading flow and fixing lint errors

Summary:
Upgrading to flow 0.91, fixing a bunch of `$FloxFixMe`s that were introduced by upgrading to 0.86.
Also fixing some linting issues.

Reviewed By: priteshrnandgaonkar

Differential Revision: D13900794

fbshipit-source-id: 5d0a1b62371f3b5d34b909bae0876583acb6f977

src/ui/components/elements-inspector/sidebar.js

@@ -81,7 +81,7 @@ type Props = {|
   client: PluginClient,
   realClient: Client,
   logger: Logger,
-  extensions?: Array<any>,
+  extensions?: Array<Function>,
 |};
 
 type State = {|
@@ -118,12 +118,8 @@ export class InspectorSidebar extends Component<Props, State> {
       return null;
     }
 
-    const sections =
+    const sections: Array<any> =
       (extensions &&
-        /* $FlowFixMe(>=0.86.0) This
-         * comment suppresses an error found when Flow v0.86 was
-         * deployed. To see the error, delete this comment and
-         * run Flow. */
         extensions.map(ext =>
           ext(
             this.props.client,