Fix projects being removed from the Workspace

We were leaving them in the workspace by accident.

src/VisualStudio/CSharp/Test/ProjectSystemShim/LifetimeTests.cs

@@ -23,6 +23,8 @@ public void DisconnectingAProjectDoesNotLeak()
 
                 project.UseReference(p => p.Disconnect());
                 project.AssertReleased();
+
+                Assert.Empty(environment.Workspace.CurrentSolution.Projects);
             }
         }
     }

src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioWorkspaceImpl.cs

@@ -1355,7 +1355,7 @@ protected internal override void OnProjectRemoved(ProjectId projectId)
                             _projectSystemNameToProjectsMap.Remove(projectName);
                         }
 
-                        return;
+                        break;
                     }
                 }