update dependencies: tomcat to 8.5.51, selenide to 5.7.0 and flexmark to 0.50.50
update dependencies: tomcat to 8.5.51, selenide to 5.7.0 and flexmark to 0.50.50

tateshitah/jspwiki,tateshitah/jspwiki,tateshitah/jspwiki,tateshitah/jspwiki