Fix sphinx-issues links

Author: tony

doc/conf.py

@@ -38,7 +38,7 @@
 releases_release_uri = "https://github.com/tmux-python/libtmux/tree/v%s"
 releases_future_release_uri = "https://github.com/tmux-python/libtmux/tree/%s"
 
-issues_github_path = about['__github__']
+issues_github_path = about['__github__'].replace('https://github.com/', '')
 
 templates_path = ['_templates']