Update version in client string for new releases

[pra-olo]

The client string set here is static and hasn't been updated in eight years.

Updating this to reflect the released version would assist SSH service operators in auditing their clients' capabilities before updating supported ciphers and key-exchange algorithms.

[Rob-Hague]

After #1256, it might be possible to achieve this by using the MSBuild WriteLinesToFile task to write out the Version property as a constant in the source. It might already be possible with WriteCodeFragment to get the AssemblyVersion attribute