fix type-o

Author: eeeebbbbrrrr

README.md

@@ -175,7 +175,7 @@ $ psql test
 
  - [cargo-pgx sub-command](cargo-pgx/)
  - [Custom Types](pgx-examples/custom_types/)
- - [Postgres Operator Funcions and Classes](pgx-examples/operators/)
+ - [Postgres Operator Functions and Operator Classes/Families](pgx-examples/operators/)
  - [Shared Memory Support](pgx-examples/shmem/)
  - [various examples](pgx-examples/)