The Wither shows white spawning animation when you move away and back again

^{Update by [Mojang] Mega_Spud (Jay Wells):}
Summary:
The Wither will show it's white spawning animation/overlay if you move far away from it and return again.

Steps to Reproduce:

1. Summon a Wither
2. Wait for the spawning animation to end
3. Teleport far away from it (/tp ~ ~ ~1000)
4. Teleport back to it (/tp ~ ~ ~-1000)

Observed Results:
The wither will be flashing white again, as if it were newly spawned.

Expected Results:
The wither should not show the spawning animation again.

Screenshots/Videos attached: Yes

Notes:

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Original Description:
Wither's birth animation will play again after you rediscover it.