Avoid use of non-ASCII in dogan plugin
Avoid use of non-ASCII in dogan plugin

Plugins get loaded in streamlink/session.py with `imp.load_module`.
`imp.load_module` uses the system locale to read the given python file.

The only way to ensure this will never fail whatever the locale the user
uses is to either:
 - Avoid imp.load_module and use something else to be determined
 - Use only ASCII characters in plugins

`imp.load_module` might be required to support both python 2 and 3
(unless an alternative exists ?).
So replace the non ASCII character with an ASCII one.

For reference, I encountered a load_module failure in the
test_plugins.py test, when loading this plugin in a containerized
environnement (LC_ALL=POSIX)

streamlink/streamlink,melmorabity/streamlink,back-to/streamlink,chhe/streamlink,gravyboat/streamlink,bastimeyer/streamlink,javiercantero/streamlink,wlerin/streamlink,beardypig/streamlink,wlerin/streamlink,bastimeyer/streamlink,beardypig/streamlink,back-to/streamlink,streamlink/streamlink,gravyboat/streamlink,chhe/streamlink,melmorabity/streamlink,javiercantero/streamlink