Removes unused "ModuleManager" (#11918)

Content.Shared/Module/IModuleManager.cs

@@ -1,19 +0,0 @@
-namespace Content.Shared.Module
-{
-    /// <summary>
-    /// Provides a simple way to check whether calling code is being run by
-    /// Robust.Client, or Robust.Server. Useful for code in Content.Shared
-    /// that wants different behavior depending on if client or server is using it.
-    /// </summary>
-    public interface IModuleManager
-    {
-        /// <summary>
-        /// Returns true if the code is being run by the client, returns false otherwise.
-        /// </summary>
-        bool IsClientModule { get; }
-        /// <summary>
-        /// Returns true if the code is being run by the server, returns false otherwise.
-        /// </summary>
-        bool IsServerModule { get; }
-    }
-}