Fix typo

Author: pquentin

docs/panels.rst

@@ -282,7 +282,7 @@ Third-party panels must subclass :class:`~debug_toolbar.panels.Panel`,
 according to the public API described below. Unless noted otherwise, all
 methods are optional.
 
-Panels can ship their own templates, static files and views. They're no public
+Panels can ship their own templates, static files and views. There is no public
 CSS API at this time.
 
 .. autoclass:: debug_toolbar.panels.Panel(*args, **kwargs)