Bump jetty.version from 12.1.5 to 12.1.6 (#751)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

pom.xml

@@ -41,7 +41,7 @@
   <properties>
     <changelist>999999-SNAPSHOT</changelist>
     <scmTag>HEAD</scmTag>
-    <jetty.version>12.1.5</jetty.version>
+    <jetty.version>12.1.6</jetty.version>
     <gitHubRepo>jenkinsci/stapler</gitHubRepo>
     <spotless.check.skip>false</spotless.check.skip>
     <ban-junit4-imports.skip>false</ban-junit4-imports.skip>