rename fill attribute

Summary:
We were using `fill={true}` as an attribute to make flexbox containers fill the entire available space.

However, `fill` is an HTML attribute (see: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/fill) This caused warnings printed to the console.

This diff renames the attribute to `grow` with is also more in line with the Flexbox terminology.

Reviewed By: priteshrnandgaonkar

Differential Revision: D10488389

fbshipit-source-id: ed8553c6203cdf6df94d26c731164ecec4c9fbd2

src/ui/components/Tabs.js

@@ -251,7 +251,7 @@ export default function Tabs(props: {|
   }
 
   return (
-    <FlexColumn fill={true}>
+    <FlexColumn grow={true}>
       <TabList>
         {before}
         {tabList}