fix(gae): remove duplicate and redundant region tags "dependencies"

[Kef131]

Description

Fixes #
b/526729539

Removes duplicate and generic dependencies region tags in appengine-java8 samples' pom.xml files. Renames the unique region tag used in devsite in endpoints-v2-skeleton/build.gradle to appengine_endpoints_gradle_dependencies to specify the gradle tool/tech used.

Checklist

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Appropriate changes to README are included in PR
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Static Analysis: mvn -P lint clean compile pmd:cpd-check spotbugs:check advisory only
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request updates region tags across several App Engine Java 8 sample projects. Specifically, in the build.gradle file for endpoints-v2-skeleton, the generic dependencies region tags are renamed to appengine_endpoints_gradle_dependencies. In several other pom.xml files (including mailgun, mailjet, memcache, pubsub, remote-client, and translate-pubsub), the generic dependencies region tags are removed entirely. I have no feedback to provide as there are no review comments to evaluate.