Update dependency NHibernate to v5.4.2

Author: renovate[bot]

src/FluentNHibernate/FluentNHibernate.csproj

@@ -11,7 +11,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="NHibernate" Version="5.3.3" />
+    <PackageReference Include="NHibernate" Version="5.4.2" />
   </ItemGroup>
 
   <ItemGroup>