Address PR feedback: SDK version to 9.0.300, remove JTF test, clean up mock file

Co-authored-by: AArnott <[email protected]>

Author: Copilot

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "8.0.116",
+    "version": "9.0.300",
     "rollForward": "patch",
     "allowPrerelease": false
   },

test/Microsoft.VisualStudio.Threading.Analyzers.Tests/AdditionalFiles/vs-threading.SyncMethodsToExcludeFromVSTHRD103.mocks.txt

@@ -1,4 +1,2 @@
 # Test exclusions for VSTHRD103 analyzer
-[System.Data.SqlClient.SqlDataReader]::Read
-[TestNamespace.TestClass]::SlowSyncMethod
-[Microsoft.VisualStudio.Threading.JoinableTaskFactory]::Run
+[TestNamespace.TestClass]::SlowSyncMethod

test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD103UseAsyncOptionAnalyzerTests.cs

@@ -1386,24 +1386,6 @@ public static void NotExcludedMethod() { }
         await CSVerify.VerifyAnalyzerAsync(test);
     }
 
-    [Fact]
-    public async Task JTFRun_ExcludedViaAdditionalFiles_GeneratesNoWarning()
-    {
-        var test = @"
-using System.Threading.Tasks;
-using Microsoft.VisualStudio.Threading;
-
-class Test {
-    async Task T() {
-        JoinableTaskFactory jtf = null;
-        jtf.Run(() => Task.CompletedTask);
-    }
-}
-";
-
-        // No diagnostic expected because JoinableTaskFactory.Run is excluded via AdditionalFiles
-        await CSVerify.VerifyAnalyzerAsync(test);
-    }
 
     private DiagnosticResult CreateDiagnostic(int line, int column, int length, string methodName)
         => CSVerify.Diagnostic(DescriptorNoAlternativeMethod).WithSpan(line, column, line, column + length).WithArguments(methodName);