fix pylint warnings of generate_how_to_cite.py

[lrineau]

Summary of Changes

Without this PR, I have locally a lot of warnings with python-3.12:

[lrineau@fernand]~/Git/cgal-master% cmake build-doc  
-- /usr/bin/python3.12
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:126: SyntaxWarning: invalid escape sequence '\c'
  title_r=title.replace("Kernel","%Kernel").replace("Interval","%Interval").replace("Matrix","%Matrix").replace("Kinetic","%Kinetic").replace("CGAL","\cgal").replace("Range","%Range")
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:127: SyntaxWarning: invalid escape sequence '\c'
  authors=authors.replace("CGAL","\cgal")
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:132: SyntaxWarning: invalid escape sequence '\c'
  <td class=\"bibtexitem\">\n "+authors+".\n "+title_r+".\n\
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:202: SyntaxWarning: invalid escape sequence '\,'
  title=match.group(1).replace("\,",",")
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:213: SyntaxWarning: invalid escape sequence '\c'
  assert len(bib)>0, "Did you forget a \cgalPkgBib{} in %r?" % filename
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:214: SyntaxWarning: invalid escape sequence '\c'
  assert len(authors)>0, "Did you forget a \cgalPkgAuthors{} in %r?" % filename
/home/lrineau/Git/cgal-master/Documentation/doc/scripts/generate_how_to_cite.py:215: SyntaxWarning: invalid escape sequence '\c'
  assert len(anchor)>0, "Did you forget the anchor in \cgalPkgDescriptionBegin{} in %r?" % filename
-- Configuring done (0.1s)
-- Generating done (0.1s)
-- Build files have been written to: /home/lrineau/Git/cgal-master/build-doc

With this PR:

[lrineau@fernand]~/Git/cgal-master% cmake build-doc                              
-- /usr/bin/python3.12
-- Configuring done (0.1s)
-- Generating done (0.1s)
-- Build files have been written to: /home/lrineau/Git/cgal-master/build-doc

I have verified that the generated how_to_cite* files are identical.

Release Management

• Affected package(s): Documentation/doc/scripts

[sloriot]

Successfully tested in CGAL-6.0-Ic-264