[BUGFIX release] Remove type export for ControllerMixin
[BUGFIX release] Remove type export for ControllerMixin

This type does not exist to be imported from the location it existed at
in the definitions, and so the types could auto-suggest an import which
would produce a runtime error. Remove it to prevent users from being
misled this way.

See also: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/62784

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