fix absence of pytest kill in Cancel Test Run

Author: Eugene Kornykhin

src/client/testing/testController/pytest/pytestExecutionAdapter.ts

@@ -246,6 +246,7 @@ export class PytestTestExecutionAdapter implements ITestExecutionAdapter {
                 });
 
                 const result = execService?.execObservable(runArgs, spawnOptions);
+                resultProc = result?.proc;
 
                 // Take all output from the subprocess and add it to the test output channel. This will be the pytest output.
                 // Displays output to user and ensure the subprocess doesn't run into buffer overflow.