[UI Tests] Disable tests involving media picker for maintenance.

[tiagomar]

Description

This PR disables UI Tests for maintenance to support the new media picker (#21190).

Tests disabled:

EditorGutenbergTests.testAddGalleryBlock()
EditorGutenbergTests.testAddMediaBlocks()
EditorGutenbergTests.testAddRemoveFeaturedImage()
EditorGutenbergTests.testBasicPostPublishWithCategoryAndTag()

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr21428-7b9635e
	Version	23.1
	Bundle ID	org.wordpress.alpha
	Commit	7b9635e
	App Center Build	WPiOS - One-Offs #6867

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[kean]

Thanks!

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr21428-7b9635e
	Version	23.1
	Bundle ID	com.jetpack.alpha
	Commit	7b9635e
	App Center Build	jetpack-installable-builds #5910

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.