fix: upgrade com.slack.api:slack-app-backend from 1.38.0 to 1.39.1

Snyk has created this PR to upgrade com.slack.api:slack-app-backend from 1.38.0 to 1.39.1.

See this package in maven:
com.slack.api:slack-app-backend

See this project in Snyk:
https://app.snyk.io/org/contentstack-devex/project/d4e249e0-1e7c-480b-9181-5e419e6d80c3?utm_source=github&utm_medium=referral&page=upgrade-pr

pom.xml

@@ -212,7 +212,7 @@
         <dependency>
             <groupId>com.slack.api</groupId>
             <artifactId>slack-app-backend</artifactId>
-            <version>1.38.0</version>
+            <version>1.39.1</version>
         </dependency> 
         <dependency>
 			<groupId>org.testng</groupId>