`update` should not be `type: Any` based on description

[jeremyfiel]

Overlay-Specification/versions/1.0.0.md

Line 125 in d029f0d

The result of the `target` JSONPath expression must be zero or more objects or arrays (not primitive types or `null` values).

This text indicates the type of update should only be object | array and not Any

[lornajane]

Good catch! In this case though, we know that there are already implementations built from the spec, and we aim to formalise the existing content. We decided against making things more restrictive (but agree this could be tightened for a future release)