Fix build warnings

### Description

There are a number of warnings that should be fixed in order to reduce the noise around the build:

- CMake configuration step warning
```
CMake Warning:
Manually-specified variables were not used by the project:

Module_ITKSimpleITKFilters
```

raised at: https://github.com/InsightSoftwareConsortium/ITKDoxygen/actions/runs/3269579446/jobs/5377237994#step:4:1148

- Build warnings/errors:
```
warning: Invalid value for 'ALIASES' tag at line 31, file /work/ITK-bld/Utilities/Doxygen/Doxyfile.Documentation: Values in list '"starteraliasnotused=@par not used" "wiki=\par Wiki Examples:
^^ \li All Media Wiki Examples ^^" "wikiexample{2}= \li \2 ^^" "endwiki=^^ ^^ ^^" "sphinx=\par ITK Sphinx Examples:
^^ \li All ITK Sphinx Examples ^^" "sphinxexample{2}=\li \2 ^^" "endsphinx=^^ ^^ ^^"' are not properly space or comma separated
```

raised at: https://github.com/InsightSoftwareConsortium/ITKDoxygen/actions/runs/3269579446/jobs/5377237994#step:4:1157

```
error: Illegal ALIASES format 'https://www.itk.org/Wiki/ITK/Examples>All Media Wiki Examples ^^'. Use "name=value" or "name{n}=value", where n is the number of arguments
error: Illegal ALIASES format '[https://www.itk.org/Wiki/ITK/Examples/\1](https://www.itk.org/Wiki/ITK/Examples//1)>\2 ^^'. Use "name=value" or "name{n}=value", where n is the number of arguments
error: Illegal ALIASES format 'https://itk.org/ITKExamples>All ITK Sphinx Examples ^^'. Use "name=value" or "name{n}=value", where n is the number of arguments
error: Illegal ALIASES format '[https://itk.org/ITKExamples/src/\1/Documentation.html](https://itk.org/ITKExamples/src//1/Documentation.html)>\2 ^^'. Use "name=value" or "name{n}=value", where n is the number of arguments
```

raised at: https://github.com/InsightSoftwareConsortium/ITKDoxygen/actions/runs/3269579446/jobs/5377237994#step:4:1158

```
warning: tag INPUT: input source '/work/ITK-bld/Documentation/Doxygen' does not exist
warning: tag INPUT: input source '/work/ITK-bld/Documentation/Doxygen/Examples.dox' does not exist
```

raised at: https://github.com/InsightSoftwareConsortium/ITKDoxygen/actions/runs/3269579446/jobs/5377237994#step:4:1162
and https://github.com/InsightSoftwareConsortium/ITKDoxygen/actions/runs/3269579446/jobs/5377237994#step:4:1163

```
Searching for files in directory /work/ITK/Modules/Registration/Metricwarning: source '/work/ITK-bld/Documentation/Doxygen' is not a readable file or directory... skipping.
warning: source '/work/ITK-bld/Documentation/Doxygen/Examples.dox' is not a readable file or directory... skipping.
```
raised at: https://github.com/InsightSoftwareConsortium/ITKDoxygen/actions/runs/3269579446/jobs/5377237994#step:4:2785

### Additional notes

These warnings are not being reported to the CDash dashboard build:
https://open.cdash.org/build/8223887

Need to be fixed in the [ITK repository](https://github.com/InsightSoftwareConsortium/ITK).

The rest of the build warnings are being tracked in: https://github.com/InsightSoftwareConsortium/ITK/issues/3654