ANW-2025 Replace https in XML namespaces with http

[abbistani]

Fix for ANW-2025, partially reverting ANW-1671

This rolls back the replacement of http with https in serializer XML namespaces, but leaves the updates to the schema locations intact.

Tested locally by doing exports of EAD, EAC, MARCXML, DC, MODS, and METS and making sure that the changes were reverted properly.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [X ] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• I have authority to submit this code.
• I have added tests to cover my changes.
• All new and existing tests passed.