Purge sRGB chunks from PNGs in examples.

Subjects each *.png file that matched grep -law "sRGB" to:
pngcrush -ow -brute -rem allb -reduce

Change-Id: Iff326d7e63d6e0106204beb1f42700032cb6b79a
Reviewed-by: Topi Reiniö <topi.reinio@theqtcompany.com>