Update unsupported verssions of .NET in diagnostics documentation

[tommcdon]

Summary

Change references to unsupported and out of date versions of .NET to currently supported versions.

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📄 File	🔗 Preview link
docs/core/diagnostics/available-counters.md	docs/core/diagnostics/available-counters
docs/core/diagnostics/compare-metric-apis.md	docs/core/diagnostics/compare-metric-apis
docs/core/diagnostics/debug-deadlock.md	docs/core/diagnostics/debug-deadlock
docs/core/diagnostics/debug-highcpu.md	docs/core/diagnostics/debug-highcpu
docs/core/diagnostics/debug-linux-dumps.md	docs/core/diagnostics/debug-linux-dumps
docs/core/diagnostics/debug-memory-leak.md	docs/core/diagnostics/debug-memory-leak
docs/core/diagnostics/debug-threadpool-starvation.md	docs/core/diagnostics/debug-threadpool-starvation
docs/core/diagnostics/debug-windows-dumps.md	docs/core/diagnostics/debug-windows-dumps
docs/core/diagnostics/diagnostic-port.md	docs/core/diagnostics/diagnostic-port
docs/core/diagnostics/diagnostics-in-containers.md	docs/core/diagnostics/diagnostics-in-containers
docs/core/diagnostics/diagnosticsource-diagnosticlistener.md	docs/core/diagnostics/diagnosticsource-diagnosticlistener
docs/core/diagnostics/dotnet-gcdump.md	docs/core/diagnostics/dotnet-gcdump
docs/core/diagnostics/event-counter-perf.md	docs/core/diagnostics/event-counter-perf
docs/core/diagnostics/eventsource-activity-ids.md	docs/core/diagnostics/eventsource-activity-ids
docs/core/diagnostics/eventsource-collect-and-view-traces.md	docs/core/diagnostics/eventsource-collect-and-view-traces
docs/core/diagnostics/eventsource-getting-started.md	docs/core/diagnostics/eventsource-getting-started
docs/core/diagnostics/eventsource-instrumentation.md	docs/core/diagnostics/eventsource-instrumentation
docs/core/diagnostics/eventsource.md	docs/core/diagnostics/eventsource
docs/core/diagnostics/metrics-collection.md	docs/core/diagnostics/metrics-collection
docs/core/diagnostics/metrics-instrumentation.md	docs/core/diagnostics/metrics-instrumentation
docs/core/diagnostics/microsoft-diagnostics-netcore-client.md	docs/core/diagnostics/microsoft-diagnostics-netcore-client
docs/core/unmanaged-api/debugging/createdebugginginterfacefromversion2-function.md	docs/core/unmanaged-api/debugging/createdebugginginterfacefromversion2-function
docs/core/unmanaged-api/profiling/icorprofilerinfo11-getenvironmentvariable-method.md	docs/core/unmanaged-api/profiling/icorprofilerinfo11-getenvironmentvariable-method
docs/core/unmanaged-api/profiling/icorprofilerinfo11-interface.md	docs/core/unmanaged-api/profiling/icorprofilerinfo11-interface
docs/core/unmanaged-api/profiling/icorprofilerinfo11-setenvironmentvariable-method.md	docs/core/unmanaged-api/profiling/icorprofilerinfo11-setenvironmentvariable-method

[BillWagner]

@tommcdon @gewarren Is this still relevant? Should we close without merging?