Remove unused usings

src/Library/ObservableComputations.Extensions/Extensions.cs

@@ -1,5 +1,4 @@
 using System.Collections.ObjectModel;
-using System.Collections.Specialized;
 using System.Linq.Expressions;
 
 namespace ObservableComputations;

src/Library/TerminalUI.Examples/Controls/ProgressBarExamples.cs

@@ -1,5 +1,4 @@
-using TerminalUI.Color;
-using TerminalUI.ConsoleDrivers;
+using TerminalUI.ConsoleDrivers;
 using TerminalUI.Controls;
 using TerminalUI.Models;
 using TerminalUI.TextFormat;