fix: upgrade org.springframework:spring-core from 5.3.19 to 5.3.39

Snyk has created this PR to upgrade org.springframework:spring-core from 5.3.19 to 5.3.39.

See this package in maven:
org.springframework:spring-core

See this project in Snyk:
https://app.snyk.io/org/cloudinaryltd/project/df8ae2e5-7514-4591-9dde-b35d56fcdb5b?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

samples/photo_album_gae/pom.xml

@@ -8,7 +8,7 @@
     <name>photo_album_gae</name>
 
     <properties>
-        <spring.version>5.3.19</spring.version>
+        <spring.version>5.3.39</spring.version>
         <appengine.app.version>1</appengine.app.version>
         <appengine.target.version>1.9.37</appengine.target.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>