Fix xref warnings

[gewarren]

Observe is an override method in a public sealed class, and protected members of public sealed classes aren't shown in the API docs, so this cross reference was causing a warning.

[ghost]

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Issue Details

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Observe is an override method in a public sealed class, and protected members of public sealed classes aren't shown in the API docs, so this cross reference was causing a warning.

Author:	gewarren
Assignees:	-
Labels:	area-System.Diagnostics
Milestone:	-

[gewarren]

Docs Build status updates of commit 73ef7f9:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Diagnostics.Metrics/Meter.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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