Suppress warnings in "invalid" test cases.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/CS6_StringInterpolation.cs

@@ -29,6 +29,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public static void InvalidFormatString(string[] args)
 		{
+#pragma warning disable IDE0043
 			Console.WriteLine(string.Format("", args.Length));
 			Console.WriteLine(string.Format("a", args.Length));
 			Console.WriteLine(string.Format("}", args.Length));
@@ -53,6 +54,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			Console.WriteLine(string.Format("{0:}", args.Length));
 			Console.WriteLine(string.Format("{0{a}0}", args.Length));
 			Console.WriteLine(string.Format("test: {0}", string.Join(",", args)));
+#pragma warning restore
 		}
 
 		public void FormattableStrings(FormattableString s, string[] args)