Remove the explicit dependency on WordPressKit

[mokagio]

Description

Building on top of wordpress-mobile/WordPressAuthenticator-iOS#836, this removes the implicit dependency on WordPressKit. That is, it removes the one import it had and removes it from Podfile.

This is not a game changer, we still depend on the library implicitly via WordPressAuthenticator. But I think it's a little win. One less library to look at in the Podfile and to be aware of.

Testing instructions

I run the app with breakpoints to verify the useURLSession value is passed along from Woo to Authenticator. The only flows that trigger WordPressKit usages are authentication ones (which is obvious given Authenticator is the the one depending on it.

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary. — N.A.

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 17.5. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

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[wpmobilebot]

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

	App Name	WooCommerce iOS
	Build Number	pr12063-710c1aa
	Version	17.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	710c1aa
	App Center Build	WooCommerce - Prototype Builds #8112

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[mokagio]

Closing as per wordpress-mobile/WordPressAuthenticator-iOS#836 (comment)