Editor: Reset search query when media picker is dismissed

[hassaanelgarem]

Part of #18840

Description

Fixes an issue in the editor where the search query was being retained even after dismissing the media picker.

Testing Instructions

1. Create a new blog post
2. Add an Image block
3. Click ADD IMAGE
4. Click WordPress Media Library
5. Search for some string that will not return any results
6. Click Cancel button in Navigation bar
7. Click ADD IMAGE
8. Click WordPress Media Library
9. Make sure that all the available images are displayed.

Regression Notes

1. Potential unintended areas of impact
   N/A
2. What I did to test those areas of impact (or what existing automated tests I relied on)
   N/A
3. What automated tests I added (or what prevented me from doing so)
   N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18980-9c33bfe on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18980-9c33bfe on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[momo-ozawa]

Works as described!