nco: Stop using xercesc3

[remkos]

Description

See: https://trac.macports.org/ticket/71310

This is to remove the linking with xercesc3 now that it has been marked as deprecated.
In fact, nco was wrongly linked to xercesc3 in the first place, since there was no code requiring it.
Its presence in the Portfile was a leftover of support for esmf, which was taken out of the port as deprecated over 2 years ago (#14756).

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 15.1 24B83 x86_64
Command Line Tools 16.1.0.0.1.1729049160

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint --nitpick?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@tenomoto for port nco.