[BUGFIX release] avoid strict assertion when object proxy calls thru for function

[toranb]

Upgrading to ember v3.1 recently I bumped into this strict assertion around ObjectProxy which broke the consumers of that addon. More details (including a full example app) and discussion w/ Robert are included in the original issue I opened last week

#16521

[rwjblue]

We discussed this exact thing at the core team meeting yesterday, and came to the same conclusion, and we are 👍 on moving forward with this tweak to the proxy assertion system.

@toranb - Two small changes here and this is good to land (and can ultimately make its way to 3.1.x):

1. Looks like the code-quality job failed, should be able to fix via yarn lint:fix.
2. Can you prefix the commit (and PR title) with [BUGFIX release]?

[toranb]

@rwjblue done and done my friend. Thanks for considering this patch for 3.1X :) I would greatly appreciate it!

[rwjblue]

Thank you!