Remove extra reference to test plan from project

[RafaelKayumov]

@joshheald spotted that there was an extra test plan file reference in project hierarchy: p1764240288217489-slack-C6H8C3G23

Removed the extra reference appeared in project root folder. The correct reference is in place and pointing to the ../Modules/Tests/NetworkingTests/RequestAuthenticatorPressureTests.xctestplan

Before	After

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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.

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 23.8. 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 Prototype by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS Prototype
	Build Number	pr16410-14efb24
	Version	23.7
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	14efb24
	Installation URL	6it8oopsm9lto

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

[joshheald]

Thanks for the quick fix