Fix GutenbergKit site media selection

[crazytonyli]

Description

Follow up review comments in #25855

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 27.1 ❄️. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

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	Build Number	33548
	Version	PR #25857
	Bundle ID	org.wordpress.alpha
	Commit	589483f
	Installation URL	31pee9r2kp42o

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	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	33548
	Version	PR #25857
	Bundle ID	com.jetpack.alpha
	Commit	589483f
	Installation URL	6ra9d0n1j852o

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