Water texture animation is considerably more jittery from 18w15a

Relates to MCPE-138121

Pretty tricky to convey this through words, but should be very easy to tell from seeing it.

In versions prior to 18w15a, water's animation was considerably smoother - the animation appeared to seamlessly fade along. From 18w15a however, the animation got considerably visually jittery, without a doubt due to its texture change.