Remove "sRGB IEC61966-2.1" profile to supress libpng warning

The above ICC profile causes the following libpng warnings while APK
packaging.

* libpng warning: iCCP: known incorrect sRGB profile
* libpng warning: iCCP: profile 'icc': 'RGB ': RGB color space not
  permitted on grayscale PNG

Bug: 11869853
Change-Id: Ida296d9e3bbd2abaae7c7500d77c8dc54d8b2382