Remove unused usings

Author: WillemJann

src/XLParser.Tests/FormulaAnalysisTest.cs

@@ -1,11 +1,7 @@
-using System;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
+using System.Collections.Generic;
 using System.Linq;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Irony.Parsing;
-using System.Globalization;
-using XLParser;
 
 namespace XLParser.Tests
 {