Remove explicit reference to Iesi.Collections (#150)

Author: hazzik

StackExchangeRedis/NHibernate.Caches.StackExchangeRedis/NHibernate.Caches.StackExchangeRedis.csproj

@@ -23,7 +23,6 @@
     <None Include="..\..\NHibernate.Caches.snk" Link="NHibernate.snk" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Iesi.Collections" Version="4.0.4" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="all" />
     <PackageReference Include="NHibernate" Version="5.2.0" />
     <PackageReference Include="StackExchange.Redis" Version="2.0.495" />