[webrtc-pc] Use consistent internal slot terminology (editorial) (#2226)

jan-ivar has just created a new issue for https://github.com/w3c/webrtc-pc:

== Use consistent internal slot terminology (editorial) ==
There are 94 matches for `.[[`, and 165 matches for `'s [[`. It's

> Set *connection*.[[CurrentLocalDescription]] to *connection*.[[PendingLocalDescription]].

vs.

> Set *connection*'s [[CurrentLocalDescription]] internal slot to *connection*'s [[PendingLocalDescription]] internal slot.

We should pick one and be consistent.

I'm partial to the former since it's more compact and predominant in [ECMAScript](https://tc39.es/ecma262/).

Thoughts?

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2226 using your GitHub account