Replace obsolete link in System.Uri

[TheLeftExit]

Summary

Updated System.Uri with a link to Uri.MakeRelativeUri in place of obsolete Uri.MakeRelative.

[opbld32]

Docs Build status updates of commit fd96647:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System/Uri.xml	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

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