Updating timeout in `SslStream_SameCertUsedForClientAndServer_Ok` to match the rest of the tests in the area.
All other passing tests standardise on `TestConfiguration.PassingTestTimeoutMilliseconds`
There seems to be no reasons for SslStream_SameCertUsedForClientAndServer_Ok` to use a hardcoded timeout.
Also the hardcoded timeout is significantly shorter and occasionally leads to failures on low-spec test VMs.
Commit migrated from https://github.com/dotnet/corefx/commit/
8919cbdd960f41ba2f87c210d5f85d0d8a3c1276