Search: Erroneously opens modal when opening a page/post preview with Classic Editor

#### Steps to reproduce the issue

1. Add Jetpack Search subscription to the site (and ensure Instant Search is enabled).
2. Install the "Classic Editor" plugin.
3. Open a page/post editor.
4. Click on "Preview Changes".

#### What I expected
For a new tab to open with a preview of the page/post.

#### What happened instead
A new tab opens with a preview of the page/post but also spawns the search modal directly on top. I suspect this has to do with the query string values added by the preview functionality.

**Screenshots**
If applicable, add screenshots to help explain your problem.

Reproduce the issue with Jetpack Search Instant Search and the Classic Editor by opening a page or post preview. Start by tracing how the preview query-string values are handled when the search modal initializes; done means the preview opens in a new tab without the modal appearing.

Written by the indexing model from the issue text.