Fix a syntax typo

Swap `` for "

pep-0505.rst

@@ -29,7 +29,7 @@ patterns involving null references.
 This PEP proposes three ``None``-aware operators for Python, based on the
 definitions and other language's implementations of those above. Specifically:
 
-* The "``None`` coalescing`` binary operator ``??`` returns the left hand side
+* The "``None`` coalescing" binary operator ``??`` returns the left hand side
   if it evaluates to a value that is not ``None``, or else it evaluates and
   returns the right hand side. A coalescing ``??=`` augmented assignment
   operator is included.