Relax python-dateutil requirement

This allows python-dateutil version 2.8.1 to be installed as required by
some pulpcore dependencies. In turn this change is a shallow workaround
to prevent pip from silently breaking Pulp when installed in the same
environment (you probably should not do that, but our test suite has this as
a hard requirement).

[noissue]

templates/python/v7.10.0/requirements.mustache

@@ -0,0 +1,15 @@
+urllib3 >= 1.25.3, < 3.0.0
+python_dateutil >= 2.8.1, < 3.0.0
+{{#asyncio}}
+aiohttp >= 3.8.4
+aiohttp-retry >= 2.8.3
+{{/asyncio}}
+{{#tornado}}
+tornado = ">= 4.2, < 5"
+{{/tornado}}
+{{#hasHttpSignatureMethods}}
+pem >= 19.3.0
+pycryptodome >= 3.9.0
+{{/hasHttpSignatureMethods}}
+pydantic >= 2
+typing-extensions >= 4.7.1