Simplify API reference

Author: gdalle

docs/src/api.md

@@ -7,22 +7,16 @@ Modules = [MetaGraphsNext]
 Pages = ["metagraph.jl"]
 ```
 
-### Undirected and directed versions
-
 ```@autodocs
 Modules = [MetaGraphsNext]
 Pages = ["metaundigraph.jl", "metadigraph.jl"]
 ```
 
-### Dictionary utilities
-
 ```@autodocs
 Modules = [MetaGraphsNext]
 Pages = ["dict_utils.jl"]
 ```
 
-### Weights
-
 ```@autodocs
 Modules = [MetaGraphsNext]
 Pages = ["weights.jl"]
@@ -35,8 +29,6 @@ Modules = [MetaGraphsNext]
 Pages = ["lightgraphs.jl"]
 ```
 
-### Overrides
-
 ```@autodocs
 Modules = [MetaGraphsNext]
 Pages = ["overrides.jl"]