[MC-225890] Potion effects don't affect player FOVs when the player is spectating an entity

The Bug

While a player is spectating another entity, such as another player, the spectator's FOV will not be affected by either the spectator itself or the spectated mob's speed/slowness effects.

To Reproduce

Summon a zombie and splash it with a potion of slowness.
Give yourself the slowness effect by using the command provided below.
```
/effect give @s minecraft:slowness infinite 10 true
```
Switch to spectator, spectate the zombie, and observe your FOV.