Fix the wrong return_url in multisite setup when using subdomains (2829)

[Narek13]

PR Description

Replace the network_home_url() with home_url() to avoid wrong return url in multisite setup.

Issue Description

When using a multisite with subdomains or top-level domains, the return URL generated by PayPal Payments always points to the main site of the network.

Steps to Reproduce

• Setup multisite network, with subdomains (top level domains)
• The store is on sub site.
• Purchase an item and pay with PayPal.
• After payment, the redirect back to the page hits the multisite main page and not the sub-page.