[SIEM] Fixed unescaped HTML entity issue (#37257)

## Summary
  * Turned on linter rule to be an error
  * Removed the extra character
  * https://github.com/elastic/ingest-dev/issues/467

Removes the extra `}` character seen after line 84 below in the screen shot:

<img width="368" alt="Screen Shot 2019-05-28 at 9 39 28 AM" src="https://user-images.githubusercontent.com/1151048/58498271-f4672f00-813a-11e9-8b80-2326db363bb0.png">

### Checklist

Use ~~strikethroughs~~ to remove checklist items you don't feel are applicable to this PR.

~~- [ ] This was checked for cross-browser compatibility, [including a check against IE11](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility)~~
~~- [ ] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/master/packages/kbn-i18n/README.md)~~
~~- [ ] [Documentation](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#writing-documentation) was added for features that require explanation or tutorials~~
~~- [ ] [Unit or functional tests](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility) were updated or added to match the most common scenarios~~
~~- [ ] This was checked for [keyboard-only and screenreader accessibility](https://developer.mozilla.org/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility#Accessibility_testing_checklist)~~

### For maintainers

~~- [ ] This was checked for breaking API changes and was [labeled appropriately](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#release-notes-process)~~
~~- [ ] This includes a feature addition or change that requires a release note and was [labeled appropriately](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#release-notes-process)~~

.eslintrc.js

@@ -553,9 +553,7 @@ module.exports = {
         'react/no-typos': 'error',
         'react/no-string-refs': 'error',
         'react/no-this-in-sfc': 'error',
-        // This can go from warn to error once this is fixed
-        // https://github.com/elastic/ingest-dev/issues/467
-        'react/no-unescaped-entities': 'warn',
+        'react/no-unescaped-entities': 'error',
         'react/no-unsafe': 'error',
         'react/no-unused-prop-types': 'error',
         'react/no-unused-state': 'error',

x-pack/plugins/siem/public/components/event_details/json_view.tsx

@@ -37,7 +37,6 @@ export const JsonView = pure<Props>(({ data }) => (
       )}
       width="100%"
     />
-    }
   </JsonEditor>
 ));