Document that .toggleClass( boolean ) has been deprecated in jQuery 3

[AurelioDeRosa]

Reference: jquery/jquery#2618.

[dmethvin]

Given that is wasn't really documented before (just a signature with no real explanation) I wonder if we should relegate this to the release notes.

[timmywil]

We've decided to save this removal for 4.0. We just need to mark it deprecated in 3.0.

[dmethvin]

Oh I missed that I guess. Yes, it's still in master so deprecate in 3.0 and remove in 4.0 then.

[AurelioDeRosa]

No worries Dave.