Removed incorrect sRGB from baxterworking.png

Running:
`rosrun baxter_examples xdisplay_image.py -f baxterworking.png`
on baxter's ruser account (or any Gentoo) would cause the warning:
"libpng warning: iCCP: known incorrect sRGB profile"
which is due to the fact that libpng-1.6 is more discerning in
checking ICC profiles in png images than in previous versions.

This was solved by running baxterworking.png through `pngcrush`:
$ pngcrush -ow -rem allb -reduce baxterworking.png
where
-ow       = overwrite input file
-rem allb = remove everything but tRNS and gAMA
-reduce   = lossless bit-depth reduction

Author: IanTheEngineer