Update after #7441

Since PR #7441 the tested versions of
Doxygen are changed from:

  - 1.8.4,
  - 1.8.13,
  - master,

to:

  - 1.8.13,
  - 1.9.6
  - master

See https://github.com/CGAL/cgal/pull/7441/files#diff-20378a17af64de2d537c278603e389b4c15fe31670621544caa850fa233ea1deR83-R84

This commit preserve the choice of Doxygen 1.8.13 as the default one for
published versions of the CGAL documentation.

Maintenance/public_release/scripts/prepare_release

@@ -42,12 +42,12 @@ printf "Copy documentation to doc_html/ and doc_html_online/...\n"
 [ -d "/srv/CGAL/www/${PUBLIC_RELEASE_NAME#CGAL-}/Manual" ] || mkdir -p "/srv/CGAL/www/${PUBLIC_RELEASE_NAME#CGAL-}/Manual"
 
 cp "$PUBLIC_RELEASE_DIR"/*(.) "${RELEASE_CANDIDATES_DIR}/$PUBLIC_RELEASE_NAME"
-files=("$MANUAL_TESTS_DIR/$INTERNAL_RELEASE"/output2/*)
+files=("$MANUAL_TESTS_DIR/$INTERNAL_RELEASE"/output1/*)
 if ((${#files[@]} == 0)); then
     printf "ERROR: documentation files are missing\n"
     error_code=1
 else
-    rsync -a --exclude xml "$MANUAL_TESTS_DIR/$INTERNAL_RELEASE"/output2/* "$DEST_DIR/doc_html/"
+    rsync -a --exclude xml "$MANUAL_TESTS_DIR/$INTERNAL_RELEASE"/output1/* "$DEST_DIR/doc_html/"
     pushd "$DEST_DIR/doc_html/Manual/search"
     for i in g n c s i; do sed -i "s/..\/BGL$i/..\/BGL\/$i/g" *; done
     popd