Remove duplicated show_symbol_type_toc key in mkdocs.yml (#90)

Author: llucax

mkdocs.yml

@@ -111,7 +111,6 @@ plugins:
             show_signature_annotations: true
             show_source: true
             show_symbol_type_toc: true
-            show_symbol_type_toc: true
             signature_crossrefs: true
           import:
             # See https://mkdocstrings.github.io/python/usage/#import for details