[releng] Update eclipse-jarsigner-plugin to 1.3.1

Up from 1.1.5. See [1] for the reason.

[1] https://www.eclipse.org/lists/cbi-dev/msg02374.html

Change-Id: Ia13a09ec79ed1cc8c047e7571d4b2a7ec41eb63e
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

pom.xml

diff --git a/pom.xml b/pom.xml
index 016dfe7..b7e5ce1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -505,7 +505,7 @@
         <plugin>
           <groupId>org.eclipse.cbi.maven.plugins</groupId>
           <artifactId>eclipse-jarsigner-plugin</artifactId>
-          <version>1.1.5</version>
+          <version>1.3.1</version>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>