Remove redundant retina scale multiplier in CCScrollLayer

For retina displays, the page indicators of CCScrollLayer are doubled in size. This has been verified with cocos2d 2.0.

For cocos2d 2.0, the point size is already multiplied with CC_CONTENT_SCALE_FACTOR by ccPointSize().

I did not test this change with cocos2d 1.0, but assume that the point size should be 6 (not 12) for a point distance of 16.