Revert "Fix how rpInfo is created in native Desktop authentication flow"

[shane-tomlinson]

This reverts commit 4172e25.

Edit: fixes #4144.

[jaredhirsch]

Adding some context:

It looks like this commit broke primaries on FxOS because it sets navigator.id = navigator.mozId, but then we try to add properties to navigator.id. In FxOS, navigator.mozId is immutable, and will silently fail if we try to modify it. This is a pretty good guess as to the cause of #4144.

[jaredhirsch]

Looks like this fix works on stage, see discussion in #4144. Merging.