Upgrade httpcore to 4.4.15

Closes gh-10626

gradle/dependency-management.gradle

@@ -139,8 +139,8 @@ dependencyManagement {
 		dependency 'org.apache.directory.shared:shared-ldap-constants:0.9.15'
 		dependency 'org.apache.directory.shared:shared-ldap:0.9.15'
 		dependency 'org.apache.httpcomponents:httpclient:4.5.13'
-		dependency 'org.apache.httpcomponents:httpcore:4.4.8'
 		dependency 'org.apache.httpcomponents:httpmime:4.5.3'
+		dependency 'org.apache.httpcomponents:httpcore:4.4.15'
 		dependency 'org.apache.mina:mina-core:2.0.0-M6'
 		dependency 'org.apache.taglibs:taglibs-standard-impl:1.2.5'
 		dependency 'org.apache.taglibs:taglibs-standard-jstlel:1.2.5'