MINOR: Update jackson to 2.9.9 (apache#6798)

Important fix: FasterXML/jackson-databind#2326

Reviewers: Colin P. McCabe <[email protected]>

Author: ijuma

gradle/dependencies.gradle

@@ -58,7 +58,7 @@ versions += [
   grgit: "3.1.1",
   httpclient: "4.5.8",
   easymock: "4.0.2",
-  jackson: "2.9.8",
+  jackson: "2.9.9",
   jacoco: "0.8.3",
   jetty: "9.4.18.v20190429",
   jersey: "2.28",