Obsolete Sync Certificate Validator Methods

[romanett]

Proposed changes

Obsolete Sync Certificate Validator Methods, as they call into the async variants anyway.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Test enhancement (non-breaking change to increase test coverage)
• Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc.
• I have signed the CLA.
• I ran tests locally with my changes, all passed.
• I fixed all failing tests in the CI pipelines.
• I fixed all introduced issues with CodeQL and LGTM.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

[codecov]

Codecov Report

❌ Patch coverage is 64.40678% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.02%. Comparing base (d25caff) to head (ae6ccbb).
⚠️ Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
...k/Opc.Ua.Core/Stack/Https/HttpsTransportChannel.cs	67.44%	14 Missing ⚠️
Libraries/Opc.Ua.Server/Server/StandardServer.cs	66.66%	2 Missing ⚠️
Libraries/Opc.Ua.Client/Session/Session.cs	0.00%	1 Missing ⚠️
...es/Opc.Ua.PubSub/Transport/MqttPubSubConnection.cs	50.00%	1 Missing ⚠️
...tack/Opc.Ua.Core/Security/Certificates/EccUtils.cs	0.00%	1 Missing ⚠️
....Ua.Core/Stack/Tcp/UaSCBinaryChannel.Asymmetric.cs	50.00%	1 Missing ⚠️
...ack/Opc.Ua.Core/Stack/Types/SoftwareCertificate.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3338      +/-   ##
==========================================
+ Coverage   51.86%   60.02%   +8.15%     
==========================================
  Files         370      371       +1     
  Lines       78618    78125     -493     
  Branches    13650    13597      -53     
==========================================
+ Hits        40779    46898    +6119     
+ Misses      33705    26919    -6786     
- Partials     4134     4308     +174     

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