[lldb][test] Correct TestIRInterpreter

In 563bea9 I misssed calling
getpid. Which still works but doesn't do what we intended.

Author: DavidSpickett

lldb/test/API/commands/expression/ir-interpreter/TestIRInterpreter.py

@@ -135,7 +135,7 @@ def test_ir_interpreter(self):
         for expression in set_up_expressions:
             self.frame().EvaluateExpression(expression, options)
 
-        func_call = "(int)getpid"
+        func_call = "(int)getpid()"
         if lldbplatformutil.getPlatform() == "windows":
             func_call = "(int)GetCurrentProcessId()"