WebUI: remove single line if rule from web style guide

TBR=michaelpg@chromium.org
BUG=916782

Change-Id: I22b4d6cefaf75d1e0331eaddb201643d5bb0d67c
Reviewed-on: https://chromium-review.googlesource.com/c/1394193
Reviewed-by: Dan Beam <dbeam@chromium.org>
Commit-Queue: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619583}

styleguide/web/web.md

@@ -309,8 +309,6 @@ Guide](https://google.github.io/styleguide/jsguide.html).
 * Use single-quotes instead of double-quotes for all strings.
     * `clang-format` now handles this automatically.
 
-* Omit curly braces for single-line if statements.
-
 * Use ES5 getters and setters
     * Use `@type` (instead of `@return` or `@param`) for JSDoc annotations on
       getters/setters