docs: Remove duplicate headers in API reference docs (#80)

Signed-off-by: Edgar Ramírez Mondragón <[email protected]>

Author: edgarrmondragon

docs/api/reference.md

@@ -4,61 +4,45 @@ Complete API documentation for the backoff module.
 
 ## Decorators
 
-###  on_exception
-
 ::: backoff.on_exception
     options:
       show_root_heading: true
       show_source: true
 
-### on_predicate
-
 ::: backoff.on_predicate
     options:
       show_root_heading: true
       show_source: true
 
 ## Wait Generators
 
-### expo
-
 ::: backoff.expo
     options:
       show_root_heading: true
       show_source: true
 
-### fibo
-
 ::: backoff.fibo
     options:
       show_root_heading: true
       show_source: true
 
-### constant
-
 ::: backoff.constant
     options:
       show_root_heading: true
       show_source: true
 
-### runtime
-
 ::: backoff.runtime
     options:
       show_root_heading: true
       show_source: true
 
 ## Jitter Functions
 
-### full_jitter
-
 ::: backoff.full_jitter
     options:
       show_root_heading: true
       show_source: true
 
-### random_jitter
-
 ::: backoff.random_jitter
     options:
       show_root_heading: true