[QUIC] Remove check for AzL3 for QUIC and H/3 tests

[ManickaP]

Fixes #123216

SymCrypt 1.9.5 is out, docker images are already fixed, let's see if the base VM images are up-to-date or need re-building.

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[Copilot]

Pull request overview

This PR removes the Azure Linux 3 VM-specific test gating that was added due to MsQuic failures, with the intent of re-enabling QUIC and HTTP/3 test execution now that SymCrypt images are expected to be updated.

Changes:

• Remove IsNotAzureLinux3VM conditions from System.Net.Quic functional test classes.
• Remove the IsNotAzureLinux3VM check from HttpClientHandlerTestBase.IsHttp3Supported.
• Delete the IsNotAzureLinux3VM helper properties that implemented the AzL3 skip logic.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs	Removes the IsNotAzureLinux3VM helper used to skip AzL3 VMs.
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicStreamTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicStreamConnectedStreamConformanceTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicListenerTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Quic/tests/FunctionalTests/QuicConnectionTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Quic/tests/FunctionalTests/MsQuicTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Quic/tests/FunctionalTests/MsQuicRemoteExecutorTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Quic/tests/FunctionalTests/MsQuicPlatformDetectionTests.cs	Attempts to remove AzL3 gating, but introduces an invalid ConditionalClass usage (see comment).
src/libraries/System.Net.Quic/tests/FunctionalTests/MsQuicCipherSuitesPolicyTests.cs	Drops AzL3 from the ConditionalClass gating list.
src/libraries/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTestBase.SocketsHttpHandler.cs	Removes the AzL3 gating from HTTP/3 support detection and deletes the helper property.