Remove "topologically sorted" documentation from ProjectDependencyGraph

These methods do not return topologically sorted results; not only
is that not something that really makes sense, but they return
IImmutableSets anyways so they have no way to guarantee ordering at all.

src/Workspaces/Core/Portable/Workspace/Solution/ProjectDependencyGraph.cs

@@ -42,7 +42,7 @@ public class ProjectDependencyGraph
         }
 
         /// <summary>
-        /// Gets the list of projects (topologically sorted) that this project directly depends on.
+        /// Gets the list of projects that this project directly depends on.
         /// </summary>
         public IImmutableSet<ProjectId> GetProjectsThatThisProjectDirectlyDependsOn(ProjectId projectId)
         {
@@ -62,7 +62,7 @@ public IImmutableSet<ProjectId> GetProjectsThatThisProjectDirectlyDependsOn(Proj
         }
 
         /// <summary>
-        /// Gets the list of projects (topologically sorted) that directly depend on this project.
+        /// Gets the list of projects that directly depend on this project.
         /// </summary> 
         public IImmutableSet<ProjectId> GetProjectsThatDirectlyDependOnThisProject(ProjectId projectId)
         {