update to BOM 7

[elharo]

@lesv since these are separate projects in the same repo, more granular PRs will help isolate issues

[elharo]

appengine-java11/guestbook-cloud-firestore

[ERROR] Failed to execute goal on project guestbook-cloud-firestore: Could not resolve dependencies for project com.example.guestbook:guestbook-cloud-firestore:war:1.0-SNAPSHOT: Could not find artifact com.example.appengine.demo:simple-jetty-main:jar:1 in central (https://repo.maven.apache.org/maven2) -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]

[elharo]

Looks like this dependency needs to be published to Maven central; either that or reconfigure the static analysis Kokoro job to install it:

    <dependency>
      <groupId>com.example.appengine.demo</groupId>
      <artifactId>simple-jetty-main</artifactId>
      <version>1</version>
      <scope>provided</scope>
    </dependency>

[lesv]

@averikitsch FYI