Accidentally a word (#11679)

Author: agjohnson

readthedocs/notifications/messages.py

@@ -98,7 +98,7 @@ def get_rendered_body(self):
     ),
     Message(
         id=BuildAppError.BUILD_TERMINATED_DUE_INACTIVITY,
-        header=_("Build terminated due inactivity"),
+        header=_("Build terminated due to inactivity"),
         body=_(
             textwrap.dedent(
                 """