(GH-1932) Remove deleted file from sln file
(GH-1932) Remove deleted file from sln file

The mkdocs.yml file is no longer required, and therefore shouldn't be
included in the sln file.

GitTools/GitVersion,ermshiperete/GitVersion,ParticularLabs/GitVersion,ermshiperete/GitVersion,GitTools/GitVersion,gep13/GitVersion,asbjornu/GitVersion,gep13/GitVersion,ermshiperete/GitVersion,ParticularLabs/GitVersion,dazinator/GitVersion,asbjornu/GitVersion,ermshiperete/GitVersion,dazinator/GitVersion