chore(deps): bump org.thymeleaf:thymeleaf in /appengine-java8/gaeinfo (#10269)

Bumps org.thymeleaf:thymeleaf from 3.1.2.RELEASE to 3.1.5.RELEASE.

---
updated-dependencies:
- dependency-name: org.thymeleaf:thymeleaf
  dependency-version: 3.1.5.RELEASE
  dependency-type: direct:production
...

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appengine-java8/gaeinfo/pom.xml

@@ -80,7 +80,7 @@ Copyright 2017 Google Inc.
     <dependency>
       <groupId>org.thymeleaf</groupId>
       <artifactId>thymeleaf</artifactId>
-      <version>3.1.2.RELEASE</version>
+      <version>3.1.5.RELEASE</version>
     </dependency>
 
   </dependencies>