Upgrade flow to 0.64 (#3899)

* Upgrade flow to 0.64

This also enables spread operator on jsx on the flow parser:

```js
<div>{...list}</div>
```

I had no idea it was even a thing.

I had to comment out a flow test that no longer parses, but it's no longer in the flow repo and the comment said that it shouldn't be working anyway so I don't think it's going to be a problem.

* Fix build script

scripts/build/rollup.parser.config.js

@@ -24,7 +24,7 @@ export default Object.assign(baseConfig, {
     // by its value before bundling.
     parser.endsWith("flow")
       ? replace({
-          "require(s8)": 'require("fs")',
+          "require(tf)": 'require("fs")',
           include: "node_modules/flow-parser/flow_parser.js"
         })
       : {},