Replace some uses of 8.0 with 9.0 in build.proj

Author: dmiller

Clojure/build.proj

@@ -24,7 +24,7 @@
 
   <PropertyGroup>	
 
-	<TestTargetFramework Condition=" '$(TestTargetFramework)' == '' ">net8.0</TestTargetFramework>
+	<TestTargetFramework Condition=" '$(TestTargetFramework)' == '' ">net9.0</TestTargetFramework>
 
 	<Error Condition=" '$(TestTargetFramework)' != 'net462' AND '$(TestTargetFramework)' != 'net9.0' AND '$(TestTargetFramework)' != 'net8.0' AND '$(TestTargetFramework)' != 'net6.0'"/>