[dotnet] Correct product version in http user agent

[nvborisenko]

Description

It puts correct version in http request header like 4.9.1 rather than 4.0.0. Assembly version is still 4.0.0 which is correct. It is achieved via AssemblyInformationalVersion attribute set in bazel.

Motivation and Context

Highlight correct product version to track usage of selenium.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[diemol]

Thank you, @nvborisenko!