updates for latest fsdocs

Author: Don Syme

FSharp.Core/FSharp.Core.fsproj

@@ -35,7 +35,6 @@
     <FsDocsLicenseLink>https://github.com/dotnet/fsharp/blob/master/License.txt</FsDocsLicenseLink>
     <FsDocsReleaseNotesLink>https://github.com/dotnet/fsharp/blob/master/release-notes.md</FsDocsReleaseNotesLink>
     <RepositoryType>git</RepositoryType>
-    <FsDocsNavbarPosition>fixed-left</FsDocsNavbarPosition>
     <FsDocsWarnOnMissingDocs>true</FsDocsWarnOnMissingDocs>
   </PropertyGroup>