Fix linting error.

Author: purple4reina

datadog/api/http_client.py

@@ -28,7 +28,7 @@
     urlfetch, urlfetch_errors = None, None
 
 try:
-    import urllib3
+    import urllib3  # type: ignore
 except ImportError:
     urllib3 = None
 

tox.ini

@@ -58,7 +58,6 @@ basepython = python3.8
 skip_install = true
 deps =
     mypy==0.770
-    urllib3==2.2.3
 commands =
     mypy --config-file mypy.ini datadog
     mypy --config-file mypy.ini --py2 datadog