Make Bitmap#copy docs more accurate

Bug: 121001670
Test: Only a documentation change.

Since Ied0426f6deff354df5998691703a18ddd33ccd3d, we no longer always
apply the ColorSpace to the copy.

Change-Id: I67f486e5c69abb2dd767ac3f1b0da515f9f20e69
1 file changed