chore: Minor update to Makefile to clean the example directory. (#4354)

This update addresses the issue of cleaning documentation-generated
files.

Previously, 'make clean' did not remove all content generated by 'make
html'.

Additionally, references to these files in flake8 during pre-commit
checks have been removed as they are unnecessary and confusing.

---------

Co-authored-by: pyansys-ci-bot <[email protected]>

Author: abhishekchitwar

doc/changelog.d/4354.maintenance.md

@@ -0,0 +1 @@
+Minor update to Makefile to clean the example directory.

doc/make.bat

@@ -47,7 +47,7 @@ goto end
 :clean
 echo Cleaning build directories...
 rmdir /s /q %BUILDDIR% > NUL 2>&1
-del /q %SOURCEDIR%\examples\* > NUL 2>&1
+rmdir /s /q %SOURCEDIR%\examples > NUL 2>&1
 rmdir /s /q %SOURCEDIR%\api\meshing\datamodel > NUL 2>&1
 rmdir /s /q %SOURCEDIR%\api\meshing\tui > NUL 2>&1
 rmdir /s /q %SOURCEDIR%\api\solver\datamodel > NUL 2>&1