Fix hcloud requirements.

Avoid installing hcloud on Python 3.9 since it is not supported.

changelogs/fragments/ansible-test-hcloud-constraint.yml

@@ -0,0 +1,2 @@
+bugfixes:
+    - ansible-test now limits installation of ``hcloud`` to Python 2.7 and 3.5 - 3.8 since other versions are unsupported

test/lib/ansible_test/_data/requirements/integration.cloud.hcloud.txt

@@ -1 +1 @@
-hcloud>=1.6.0 ; python_version >= '2.7' # Python 2.6 is not supported (sanity_ok); Only hcloud >= 1.6.0 supports Floating IPs with names
+hcloud>=1.6.0 ; python_version >= '2.7' and python_version < '3.9' # Python 2.6 is not supported (sanity_ok); Only hcloud >= 1.6.0 supports Floating IPs with names; Python 3.9 and later are not supported