[flake] Remove inproc thread stress tests (#32283)

These tests are failing because they're running with too few threads,
however if we give them sufficient threads to catch bugs they're flaky.

Remove them and get the team some bandwidth back.

test/cpp/end2end/thread_stress_test.cc

@@ -297,13 +297,8 @@ static void SendRpc(grpc::testing::EchoTestService::Stub* stub, int num_rpcs,
 
 typedef ::testing::Types<
     CommonStressTestSyncServer<CommonStressTestInsecure<TestServiceImpl>>,
-    CommonStressTestSyncServer<CommonStressTestInproc<TestServiceImpl, false>>,
-    CommonStressTestSyncServerLowThreadCount<
-        CommonStressTestInproc<TestServiceImpl, true>>,
     CommonStressTestAsyncServer<
-        CommonStressTestInsecure<grpc::testing::EchoTestService::AsyncService>>,
-    CommonStressTestAsyncServer<CommonStressTestInproc<
-        grpc::testing::EchoTestService::AsyncService, false>>>
+        CommonStressTestInsecure<grpc::testing::EchoTestService::AsyncService>>>
     CommonTypes;
 TYPED_TEST_SUITE(End2endTest, CommonTypes);
 TYPED_TEST(End2endTest, ThreadStress) {