DOC: Fix `vtk::ExtractSelectedPolyDataIds` class doc Doxygen syntax

Fix `vtk::ExtractSelectedPolyDataIds` class doc Doxygen syntax:
- Use the Doxygen `\code{.cpp}`/`\endcode` command to treat the block
  within them as code and therefore to apply the corresponding
  formatting.
- Do not use backticks when referring to VTK classes: the Doxygen
  automatic link generation highlights the class names natively.
- Use the Doxygen `\verbatim`/`\endverbatim` command to treat the block
  within them as a verbatim text and therefore to apply the
  corresponding formatting.
- Fix the class name cases so that they can be automatically recognized
  as such and Doxygen can link them to their class documentation.

Take advantage of the commit to:
- Reword a description for the sake of clearliness.
- Start sentences with capitals.

Filters/Extraction/vtkExtractSelectedPolyDataIds.h

@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: BSD-3-Clause
 /**
  * @class   vtkExtractSelectedPolyDataIds
- * @brief   extract a list of cells from a polydata
+ * @brief   Extract a list of cells from a polydata.
  *
  * vtkExtractSelectedPolyDataIds extracts all cells in vtkSelection from a
  * vtkPolyData.
@@ -11,21 +11,25 @@
  * vtkSelection
  *
  * @deprecated vtkExtractSelectedPolyDataIds is deprecated in VTK 9.2 and will be removed.
- * Use `vtkExtractSelection` instead of `vtkExtractSelectedPolyDataIds`.
+ * Use vtkExtractSelection instead of vtkExtractSelectedPolyDataIds.
  *
  * Example using vtkExtractSelectedPolyDataIds:
  *
+ * \code{.cpp}
  * vtkNew<vtkExtractSelectedPolyDataIds> selFilter;
  * selFilter->SetInputConnection(0, sphereSource->GetOutputPort());
  * selFilter->SetInputConnection(1, selectionSource->GetOutputPort());
+ * \endcode
  *
  * Example using vtkExtractSelection:
- *
+ * \code{.cpp}
  * vtkNew<vtkExtractSelection> selFilter;
  * selFilter->SetInputConnection(0, sphereSource->GetOutputPort());
  * selFilter->SetInputConnection(1, selectionSource->GetOutputPort());
+ * \endcode
  *
- * convert selFilter's output from vtkUnstructuredGrid to vtkPolydata
+ * The above codes convert \verbatim selFilter \endverbatim 's output from vtkUnstructuredGrid
+ * to vtkPolyData.
  */
 
 #ifndef vtkExtractSelectedPolyDataIds_h