update eclipse-jarsigner-plugin to 1.3.1

Change-Id: Id75aa867438e154b833be39b1a2d8a115e0491c2
diff --git a/pom.xml b/pom.xml
index eb1cc10..db778c3 100644
--- a/pom.xml
+++ b/pom.xml
@@ -23,7 +23,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <tycho.scmUrl>scm:git:https://git.eclipse.org/r/p/usssdk/org.eclipse.usssdk.git</tycho.scmUrl>
     <tycho-version>1.6.0</tycho-version>
-    <jarsigner-version>1.1.7</jarsigner-version>
+    <jarsigner-version>1.3.1</jarsigner-version>
 
     <!-- OS-specific JVM flags, empty for the default case but redefined below -->
     <os-jvm-flags/>