fix(upgrade): missing parenthesis in RxJs compat warning

[Splaktar]

Fixes

This project uses a temporary compatibility version of RxJs (5.6.0-forward-compat.4.

Please visit the link below to find instructions on how to update RxJs.
https://docs.google.com/document/d/12nlLt71VLKb-z3YaSGzUfx6mJbc34nsMXtByPUN35cg/edit#

[clydin]

Commit message should start with fix(@angular/cli):

[Splaktar]

@clydin OK, thank you for that information. I'll try to remember it for next time.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}