Simplify Multi-Release plugin jar patch

We don't have to worry about running on Java <9 anymore.

patches/api/Enable-multi-release-plugin-jars.patch

@@ -13,18 +13,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
          this.dataFolder = dataFolder;
          this.file = file;
 -        this.jar = new JarFile(file);
-+        // Paper - enable multi-release jars for Java 9+
-+        JarFile jarFile;
-+        try {
-+            final java.lang.reflect.Method runtimeVersionMethod = JarFile.class.getMethod("runtimeVersion");
-+            final Object runtimeVersion = runtimeVersionMethod.invoke(null);
-+            @SuppressWarnings("JavaReflectionMemberAccess") final java.lang.reflect.Constructor<JarFile> constructor = JarFile.class.getConstructor(File.class, boolean.class, int.class, runtimeVersion.getClass());
-+            jarFile = constructor.newInstance(file, true, java.util.zip.ZipFile.OPEN_READ, runtimeVersion);
-+        } catch (Exception ignored) {
-+            jarFile = new JarFile(file);
-+        }
-+        this.jar = jarFile;
-+        // Paper end
++        this.jar = new JarFile(file, true, java.util.zip.ZipFile.OPEN_READ, JarFile.runtimeVersion()); // Paper - enable multi-release jars for Java 9+
          this.manifest = jar.getManifest();
          this.url = file.toURI().toURL();
          this.libraryLoader = libraryLoader;