publisher: correct homepage update call to use api prefix

Updates adding prefixes into the publisher [1] failed to update the put
call used to update a space's homepage; correcting.

[1]: d920ee7

Signed-off-by: James Knight <james.d.knight@live.com>

sphinxcontrib/confluencebuilder/publisher.py

@@ -1169,7 +1169,7 @@ def update_space_home(self, page_id):
         else:
             page = self.rest.get(f'{self.APIV1}content/{page_id}', None)
         try:
-            self.rest.put('space', self.space_key, {
+            self.rest.put(f'{self.APIV1}space', self.space_key, {
                 'key': self.space_key,
                 'name': self.space_display_name,
                 'homepage': page,