[lib/Syntax] Rename an API, accesor->accessor.

The latter is the correct way.

Author: Davide Italiano

utils/gyb_syntax_support/DeclNodes.py

@@ -371,7 +371,7 @@
              Child('Pattern', kind='Pattern'),
              Child('TypeAnnotation', kind='TypeAnnotation', is_optional=True),
              Child('Initializer', kind='InitializerClause', is_optional=True),
-             Child('Accesor', kind='AccessorBlock', is_optional=True),
+             Child('Accessor', kind='AccessorBlock', is_optional=True),
              Child('TrailingComma', kind='CommaToken', is_optional=True),
          ]),