Fixed a typographical error

Fix Version History and Copyright headings level under Lifespan Protocol chapter.

Author: ryomahan

specs/lifespan.rst

@@ -122,14 +122,14 @@ Keys:
 
 
 Version History
-===============
+'''''''''''''''
 
 * 2.0 (2019-03-04): Added startup.failed and shutdown.failed,
   clarified exception handling during startup phase.
 * 1.0 (2018-09-06): Updated ASGI spec with a lifespan protocol.
 
 
 Copyright
-=========
+'''''''''
 
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