The white pixels are still present when having any resource pack loaded, even the programmer art pack from Mojang.
This issue was marked as fixed in 219211, but it still wasn't fixed.
In 223882 it was marked as won't fix, in 225972 it was marked invalid with a comment from a moderator saying, "Update your pack then" with no explanation on what to do.
This problem is still happening and the only way to fix it is to color those 2 pixels the same color as you want them for both, attached below is how I did it for my pack. It would be nice if Mojang fixed this or gave information on how to "Update your pack" to fix this.
If your pack has this, it's because there are partially transparent pixels in that area that are rendered as solid. Simply get rid of those pixels, or don't add them in the first place.