Use utf-8 instead of utf-7 in server.py

Not sure whether this is by intention or a typo, but with utf-7 I get:

```python
    from plone.act.variables import PLONE_URL
  File "/Users/jone/projects/packages/eGov/src/plone.act/src/plone/act/__init__.py", line 4, in <module>
    from plone.act.server import Zope2ServerLibrary
ZopeXMLConfigurationError: File "<string>", line 1.115-1.256
    SyntaxError: 'utf7' codec can't decode byte 0x2f in position 39: unexpected special character (server.py, line 55)
```