Migrate in-store-pickup email to strict mode

[smartexcan]

Description (*)

The In Store Pickup "Ready for pickup" notification email still used deprecated (and removed as of magento 2.4.4) variables with direct method calls.
This resulted in the affected variables in the email template not being rendered.

Fixed Issues (if relevant)

1. Fixes In Store Pickup email still using legacy methods #3384

Manual testing scenarios (*)

1. Create order with in-store-pickup
2. Send ready for pickup email
3. Check email output for customer name.

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds are green)