Remove outdated comment from Rect
Remove outdated comment from Rect

This has changed after #3787.

The packed attribute was added in
75aac5bc02f07f1b1b1814e488926d22173e3594 for _NET_WORKAREA. However,
eec80838ab39377f18e3f68dc8a27923ae19e57e removed _NET_WORKAREA support.
I did some quick greping for `memcpy.+Rect` and didn't find any similar
code that could theoretically lead to problems.

stapelberg/i3,Airblader/i3-original,Airblader/i3-original,Airblader/i3,i3/i3,Airblader/i3,stapelberg/i3,i3/i3,i3/i3,Airblader/i3-original,Airblader/i3-original,Airblader/i3-original,i3/i3,Airblader/i3,stapelberg/i3,Airblader/i3,stapelberg/i3