Fix an unnecessary thread pool dependency when waiting JTF collection.

It leads slowdown during solution closing time.

src/Microsoft.VisualStudio.Threading/JoinableTaskCollection.cs

@@ -175,7 +175,7 @@ public async Task JoinTillEmptyAsync(CancellationToken cancellationToken)
 
             using (this.Join())
             {
-                await this.emptyEvent.WaitAsync(cancellationToken).ConfigureAwait(false);
+                await this.emptyEvent.WaitAsync(cancellationToken).ConfigureAwaitRunInline();
             }
         }