W-22202552: Add CloudHub Network Administrator permission note for traffic switching

[kevintroller]

Summary

• Adds a [NOTE] block to the CloudHub to CloudHub 2.0 Application Migration page (app-migration.adoc) stating that the CloudHub Network Administrator permission is required for traffic switching.
• Without this permission, users cannot access the traffic switching controls.

Test plan

• Verify the note renders correctly on the published page under the "Next Steps After Application Upgrade" section.
• Confirm the xref link to permissions-by-product resolves properly.

GUS: W-22202552

[hannanelson]

Suggested change

	To switch application traffic, you must have the *CloudHub Network Administrator* permission. Without this permission, the traffic switching controls are not available. For more information about assigning permissions, see xref:access-management::permissions-by-product.adoc[Permissions Available in Anypoint Platform].
	To switch application traffic, you must have the CloudHub Network Administrator permission. Without this permission, the traffic switching controls aren't available. For more information about assigning permissions, see xref:access-management::permissions-by-product.adoc[].