Upgrade to JDK 13 (#5427)

Author: LinusDietz

.github/workflows/deployment.yml

@@ -45,7 +45,7 @@ jobs:
     - name: Set up JDK
       uses: actions/setup-java@v1
       with:
-        java-version: 12.0.2
+        java-version: 13
     - uses: actions/cache@v1
       with:
         path: ~/.gradle/caches

.travis.yml

@@ -1,6 +1,6 @@
 language: java
 jdk:
-  - openjdk12
+  - openjdk13
 
 # we test at Ubuntu Trusty (Ubuntu 14.04 LTS)
 # see https://docs.travis-ci.com/user/trusty-ci-environment/

build.gradle

@@ -23,7 +23,7 @@ plugins {
     id 'com.github.ben-manes.versions' version '0.27.0'
     id 'org.javamodularity.moduleplugin' version '1.5.0'
     id 'org.openjfx.javafxplugin' version '0.0.8'
-    id 'org.beryx.jlink' version '2.16.2'
+    id 'org.beryx.jlink' version '2.16.3'
 }
 
 gradle.startParameter.showStacktrace = org.gradle.api.logging.configuration.ShowStacktrace.ALWAYS
@@ -42,8 +42,10 @@ apply from: 'eclipse.gradle'
 
 group = "org.jabref"
 version = "5.0.0"
-sourceCompatibility = 12
-targetCompatibility = 12
+
+sourceCompatibility = 13
+targetCompatibility = 13
+
 mainClassName = "$moduleName/org.jabref.JabRefLauncher"
 
 // TODO: Ugly workaround to temporarily ignore build errors to dependencies of latex2unicode