Enable a string test for overload

Author: certik

integration_tests/test_generics_01.py

@@ -26,8 +26,7 @@ def test(a: bool) -> i32:
 def check():
     assert foo(2) == 4
     assert foo(2, 10) == 20
-    # Following assert has LLVM string len issue: gh-175
-    # assert foo("hello") == "lpython-hello"
+    assert foo("hello") == "lpython-hello"
     assert test(10) == 20
     assert test(False) == -test(True) and test(True) == 10