Fix: CI break

CI builds cannot use C# 13.0, reverting to C# 12.0

Author: uxmal

src/Gui/Gui.csproj

@@ -8,7 +8,7 @@
     <RootNamespace>Reko.Gui</RootNamespace>
     <AssemblyName>Reko.Gui</AssemblyName>
     <Configurations>Debug;Release</Configurations>
-    <LangVersion>10.0</LangVersion>
+    <LangVersion>12.0</LangVersion>
     <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>

src/UnitTests/Arch/Infineon/M8C/M8CDisassemblerTests.cs

@@ -22,9 +22,6 @@
 using Reko.Arch.Infineon;
 using Reko.Arch.Infineon.M8C;
 using Reko.Core;
-using Reko.Core.Memory;
-using System;
-using System.Text;
 
 namespace Reko.UnitTests.Arch.Infineon.M8C;
 

src/tools/regressionTests/regressionTests.csproj

@@ -3,7 +3,6 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net8.0</TargetFramework>
-    <LangVersion>13.0</LangVersion>
     <nullable>enable</nullable>
     <AssemblyName>regressionTests</AssemblyName>
     <RootNamespace>Reko.Tools.regressionTests</RootNamespace>