fix: remove all keys

Author: Sudrut

src/content/docs/cpp/language/functions.mdx

@@ -2,8 +2,6 @@
 title: Overview
 sidebar:
   order: 1
-cppdoc:
-  keys: ["cpp.lang.functions"]
 ---
 
 import { Revision, RevisionBlock } from "@components/revision";

src/content/docs/cpp/language/functions/default_arguments.mdx

@@ -2,8 +2,6 @@
 title: Default arguments
 sidebar:
   order: 3
-cppdoc:
-  keys: ["cpp.lang.functions.default_arguments"]
 ---
 
 import { Decl, DeclDoc } from "@components/decl-doc";

src/content/docs/cpp/language/functions/function.mdx

@@ -2,8 +2,6 @@
 title: Function declaration
 sidebar:
   order: 2
-cppdoc:
-  keys: ["cpp.lang.functions.function"]
 ---
 
 import { Decl, DeclDoc } from "@components/decl-doc";

src/content/docs/cpp/language/functions/variadic_arguments.mdx

@@ -2,8 +2,6 @@
 title: Variadic arguments
 sidebar:
   order: 4
-cppdoc:
-  keys: ["cpp.lang.functions.variadic_arguments"]
 ---
 
 import { Decl, DeclDoc } from "@components/decl-doc";