Update Animator.yaml (#1078)

## Changes

<!-- Please summarize your changes. -->
put a note under LoadAnimation documenting possible hard error

<!-- Please link to any applicable information (forum posts, bug
reports, etc.). -->
I ran into this cryptic error "Cannot load the AnimationClipProvider
Service." when trying to load an animation. I did some searching and the
root cause seems to be calling load animation on an animator that isnt
yet parented to the workspace. I have no clue why this is a necessity at
all, let alone pressing enough to warrant a hard error. This seems to be
a long standing problem that occurs on occasion for humanoids and the
regular player model as well, causing some users to have broken
animations from the default animation script erroring. See this thread

https://devforum.roblox.com/t/error-cannot-load-the-animationclipprovider-service/1639315/98
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---------

Co-authored-by: IgnisRBX <[email protected]>

Author: lack-of-gravity-jack

content/en-us/reference/engine/classes/Animator.yaml

@@ -169,6 +169,10 @@ methods:
       `Class.BasePart:SetNetworkOwner()`, this function also loads the animation
       for the server as well.
 
+      Note that the `Class.Animator` must be in the `Class.Workspace` before
+      making a call to `LoadAnimation()` or else it will be unable to retrieve
+      the `Class.AnimationClipProvider` service and throw an error.
+
       You should use this function directly instead of the similarly-named
       `Class.Humanoid:LoadAnimation()` and
       `Class.AnimationController:LoadAnimation()` functions. These are