OAK-8502: oak-examples/standalone: update spring boot dependency to 1.5.21
OAK-8502: oak-examples/standalone: update spring boot dependency to 1.5.21

git-svn-id: 67138be12999c61558c3dd34328380c8e4523e73@1863634 13f79535-47bb-0310-9956-ffa450edef68

amit-jain/jackrabbit-oak,amit-jain/jackrabbit-oak,trekawek/jackrabbit-oak,amit-jain/jackrabbit-oak,apache/jackrabbit-oak,trekawek/jackrabbit-oak,anchela/jackrabbit-oak,trekawek/jackrabbit-oak,mreutegg/jackrabbit-oak,mreutegg/jackrabbit-oak,trekawek/jackrabbit-oak,mreutegg/jackrabbit-oak,anchela/jackrabbit-oak,amit-jain/jackrabbit-oak,apache/jackrabbit-oak,amit-jain/jackrabbit-oak,mreutegg/jackrabbit-oak,anchela/jackrabbit-oak,trekawek/jackrabbit-oak,mreutegg/jackrabbit-oak,apache/jackrabbit-oak,apache/jackrabbit-oak,apache/jackrabbit-oak,anchela/jackrabbit-oak,anchela/jackrabbit-oak