update test as casing is not all lower

Author: Oren Novotny

src/GitVersionExe.Tests/HelpWriterTests.cs

@@ -16,6 +16,7 @@ public void AllArgsAreInHelp()
             { "TargetBranch", "/b" },
             { "LogFilePath" , "/l" },
             { "DynamicRepositoryLocation" , "/dynamicRepoLocation" },
+            { "ExcludeUpdateAssemblyVersion" , "/excludeUpdateAssemblyVersion" },
             { "IsHelp", "/?" }
         };
         string helpText = null;