I'm no expert but I believe C106 is basically in parallel with the width coil(T4) so I would suspect it was included to increase the width by partially cancelling the effect of T4. So long as you're getting the desired width I wouldn't worry about removing it. If you're curious what it's doing you could even play with it's value. You may see some change horz linearity. Most everything in the horizontal circuit interacts to some extent. Oh, I've been an active fixed wing RC'er for about 45 years.
