Fixed typo in the help command

Author: jeanfi

gh-md-toc

@@ -323,7 +323,7 @@ show_help() {
     echo "  --indent <NUM>      Set indent size. Default: 3."
     echo "  --insert            Insert new TOC into original file. For local files only. Default: false."
     echo "                      See https://github.com/ekalinin/github-markdown-toc/issues/41 for details."
-    echo "  --no-backup         Remove backup file. Set --insert as well. Defaul: false."
+    echo "  --no-backup         Remove backup file. Set --insert as well. Default: false."
     echo "  --hide-footer       Do not write date & author of the last TOC update. Set --insert as well. Default: false."
     echo "  --skip-header       Hide entry of the topmost headlines. Default: false."
     echo "                      See https://github.com/ekalinin/github-markdown-toc/issues/125 for details."