remove `cy.window().its('angular')` from its doc

## I'm submitting a...

```
[ ] Bug report
[x] Content update
[ ] Process update (build, deployment, ... )
```

## Type of bug / changes

I don't believe this works in newer versions of Angular - furthermore, we shouldn't give examples for the cy.window() that are reliant on outside frameworks - our examples should access props that we know are accessible regardless of 3rd parties. 