Improve dismissal of `createPost` pattern overlay on pages.

[peterwilsoncc]

Describe the bug

Currently the createPost function attempts to dismiss pattern overlay on pages after waiting for 1500ms.

This is a little flaky as the overlay can sometimes take longer to appear so the function will proceed before the pattern exists.

I'm seeing this happen most commonly on trunk so I suspect something has changed in WordPress that is slowing down the appearance of the overlay recently.

Steps to Reproduce

1. Configure wp-env to use "core":"WordPress/WordPress#master"
2. Create a test to create a page
3. Run the create post tests
4. Hope it takes a little while
5. Re-run if not.

If the test continues to pass, then change this line to wait for 50ms

cypress-wp-utils/src/commands/create-post.ts

Line 73 in 55454f6

cy.wait(1500);

Screenshots, screen recording, code snippet

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Environment information

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WordPress information

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