Update docs/docs/diff.md

Co-authored-by: Ben Noordhuis <[email protected]>

Author: saghul

docs/docs/diff.md

@@ -43,7 +43,7 @@ use a JIT, several significant performance improvements have been made:
 - Opcode fusion
 - Polymorphic inline caching
 - Memory allocation improvements
-- Improved variable resolver
+- Improved parse speeds
 
 ## New ECMAScript APIs