[wasm][aot][tests] Disable tests causing crash - System.Text.Encoding…

[radical]

…s.Web.Tests

With these tests disabled, the test run doesn't crash, and can be
reenabled for AOT.

Issue: #50965

[ghost]

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Issue Details

---

…s.Web.Tests

With these tests disabled, the test run doesn't crash, and can be
reenabled for AOT.

Issue: #50965

Author:	radical
Assignees:	-
Labels:	arch-wasm, area-Codegen-AOT-mono, wasm-aot-test
Milestone:	-

[radical]

Libraries Build windows allConfigurations x64 Debug is failing with unrelated error:

  Failed to download package 'runtime.linux-arm64.runtime.native.System.IO.Ports.6.0.0-preview.6.21307.1' from 'https://pkgs.dev.azure.com/dnceng/9ee6d478-d288-47f7-aacc-f6e6d082ae6d/_packaging/825db618-e3eb-4426-ba54-b1d6e6c944d8/nuget/v3/flat2/runtime.linux-arm64.runtime.native.system.io.ports/6.0.0-preview.6.21307.1/runtime.linux-arm64.runtime.native.system.io.ports.6.0.0-preview.6.21307.1.nupkg'.
  The SSL connection could not be established, see inner exception.
    Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..
    An existing connection was forcibly closed by the remote host.