Remove warnings in test cases.

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

@@ -16,6 +16,8 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+#pragma warning disable CS9113
+
 using System;
 using System.Collections.Generic;
 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3452.cs

@@ -1,3 +1,5 @@
+#pragma warning disable CS9124
+
 using System;
 
 namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3610.cs

@@ -1,3 +1,5 @@
+#pragma warning disable CS9124
+
 using System;
 using System.Collections.Generic;