Clean up empty documentation pages and sections

CHANGELOG.md

@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - `MeshcatVisualizer` doesn't crash anymore when there is no collision model defined ([#2147](https://github.com/stack-of-tasks/pinocchio/pull/2147))
 - Fix MSVC build ([#2155](https://github.com/stack-of-tasks/pinocchio/pull/2155))
 - Fix stub generation ([#2166](https://github.com/stack-of-tasks/pinocchio/pull/2166))
+- Clean up empty documentation pages and sections ([#2167](https://github.com/stack-of-tasks/pinocchio/pull/2167))
 
 ### Added
 - Add `examples/floating-base-velocity-viewer.py` to visualize floating base velocity [#2143](https://github.com/stack-of-tasks/pinocchio/pull/2143)

doc/treeview.dox

@@ -70,21 +70,6 @@ namespace pinocchio {
        - \subpage md_doc_d-practical-exercises_7-learn
   */
 
-  /** \page md_doc_e-implementation_intro Implementation / Technical details
-        - \subpage md_doc_e-implementation_a-overview
-        - \subpage md_doc_e-implementation_b-sparsity
-        - \subpage md_doc_e-implementation_c-crtp
-        - \subpage md_doc_e-implementation_d-miscs
-  */
-
-  /** \page md_doc_f-benchmarks_intro Benchmarks
-        - \subpage md_doc_f-benchmarks_a-overview
-        - \subpage md_doc_f-benchmarks_b-howto
-  */
-
-  /** \page md_doc_g-success-stories_intro Success Stories
-  */
-
   //
   // Modules organization
   //