[chassis][voq] Remove the leaf ref for the ifname in sonic-system-port.yang

[arlakshm]

Why I did it

Work item tracking

• Microsoft ADO 27934751:

How I did it

Fixes #18854 Update the sonic-system-port.yang to remove the check to have ifname as leafref in the port table The system-port config table will have all the ports in the chassis not only to one linecard, so in case of the chassis with different linecards sku with different number of ports this leafref will not work.

Which release branch to backport (provide reason below if selected)

• [ ] 201811
• [ ] 201911
• [ ] 202006
• [ ] 202012
• [ ] 202106
• [ ] 202111
• [ ] 202205
• [ ] 202211
• [ ] 202305

Tested branch (Please provide the tested image version)

• [ ]
• [ ]

Description for the changelog

Link to config_db schema for YANG module changes

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