Update Humanoid.yaml (#864)

## Changes

Changes the description for the Humanoid object to say "Roblox
experience", rather than "Roblox level" as "experience" much better fits
the context of the writing.

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

@@ -7,7 +7,7 @@ summary: |
 description: |
   The Humanoid is a special object that gives models the functionality of a
   character. It grants the model with the ability to physically walk around and
-  interact with various components of a Roblox level. Humanoids are always
+  interact with various components of a Roblox experience. Humanoids are always
   parented inside of a `Class.Model`, and the model is expected to be an
   assembly of `Class.BasePart` and `Class.Motor6D`; the root part of the
   assembly is expected to be named `HumanoidRootPart`. It also expects a part