add discussion of canopy dieback events (?)

[teixeirak]

From R2: "I read this review keenly interested in what these known aspects would mean for the interactions amongst leaf traits and sensitivity to temperature, tie them back to some empirical findings of more recent vintage, and possibly to gain some insights into canopy dieback phenomena during heat events or with climate warming. In the end, the latter weren’t discussed but the authors are applauded for taking on such a huge topic. Fig. 1 is a useful entrée to the subject area."

[teixeirak]

@NidhiVinod , if possible I think it would be good to add some content on this.

[NidhiVinod]

@teixeirak, I have added a few lines on canopy die-back but please let me know if that should elaborated

[teixeirak]

To me, that's sufficient. I simplified the sentence a bit.

Closing this now.