Update dependency org.jetbrains.kotlin:kotlin-stdlib-jdk8 to v1.3.60 (GoogleCloudPlatform#494)

Co-authored-by: Les Vogel <[email protected]>

Author: renovate-bot

appengine-standard-java8/kotlin-sb-appengine-standard/pom.xml

@@ -68,7 +68,7 @@ limitations under the License.
     <dependency>
       <groupId>org.jetbrains.kotlin</groupId>
       <artifactId>kotlin-stdlib-jdk8</artifactId>
-      <version>1.3.50</version>
+      <version>1.3.60</version>
     </dependency>
     <dependency>
       <groupId>org.jetbrains.kotlin</groupId>