Rename GuildRegion to VoiceRegion.

This naming makes more sense since voice regions are not a guild
exclusive concept.

discord/calls.py

@@ -27,7 +27,7 @@ DEALINGS IN THE SOFTWARE.
 import datetime
 
 from . import utils
-from .enums import GuildRegion, try_enum
+from .enums import VoiceRegion, try_enum
 from .member import VoiceState
 
 class CallMessage:
@@ -91,7 +91,7 @@ class GroupCall:
         Denotes if this group call is unavailable.
     ringing: List[:class:`User`]
         A list of users that are currently being rung to join the call.
-    region: :class:`GuildRegion`
+    region: :class:`VoiceRegion`
         The guild region the group call is being hosted on.
     """
 
@@ -106,7 +106,7 @@ class GroupCall:
         self._update(**kwargs)
 
     def _update(self, **kwargs):
-        self.region = try_enum(GuildRegion, kwargs.get('region'))
+        self.region = try_enum(VoiceRegion, kwargs.get('region'))
         lookup = {u.id: u for u in self.call.channel.recipients}
         me = self.call.channel.me
         lookup[me.id] = me