fix: fix .close() (#1231)

Call `self._http.close()`, since `google_auth_httplib2.AuthorizedHttp` (https://github.com/googleapis/google-auth-library-python-httplib2/commit/feda187133beeb656fdd7f30ed124ed1e428a74a) has been fixed to also have a `close` method like `httplib2.Http()`


Fixes #1046 🦕
diff --git a/setup.py b/setup.py
index b95495b..80362d8 100644
--- a/setup.py
+++ b/setup.py
@@ -34,7 +34,7 @@
 install_requires = [
     "httplib2>=0.15.0,<1dev",
     "google-auth>=1.16.0,<2dev",
-    "google-auth-httplib2>=0.0.3",
+    "google-auth-httplib2>=0.1.0",
     "google-api-core>=1.21.0,<2dev",
     "six>=1.13.0,<2dev",
     "uritemplate>=3.0.0,<4dev",