DOCS-33261: Add note that Java SDK is in Maintenance Mode

[cbullinger]

Pull Request Info

Indicate to users that the Java SDK is in a best-effort maintenance mode and no longer receiving any new features.

And, per Slack convo, confirm you can use other SDKs in a Java project.

Jira

• https://jira.mongodb.org/browse/DOCSP-33261

Staged Changes

• Java SDK landing
• Install - Java SDK

Reminder Checklist

If your PR modifies the docs, you might need to also update some corresponding
pages. Check if completed or N/A.

• Create Jira ticket for corresponding docs-app-services update(s), if any
• Checked/updated Admin API
• Checked/updated CLI reference

Review Guidelines

REVIEWING.md

[github-actions]

Readability for Commit Hash: 27ec16c

You can see any previous Readability scores (if they exist) by looking
at the comment's history.

Readability scores for changed documents:

• source/sdk/java: Grade Level: 11.2, Reading Ease: 34.63
• source/sdk/java/install: Grade Level: 9.7, Reading Ease: 44.0

For Grade Level, aim for 8 or below.

For Reading Ease scores, aim for 60 or above:

Score	Difficulty
90-100	Very Easy
80-89	Easy
70-79	Fairly Easy
60-69	Medium
50-59	Fairly Hard
30-49	Hard
0-29	Very Hard

For help improving readability, try Hemingway App.

[MongoCaleb]

LGTM

[docs-builder-bot]

✨ Staging URL: https://preview-mongodbmongodb.gatsbyjs.io/realm/master/

🪵 Logs

• job log: 4b0f02ffc8120d561318cbe5ec5d1019702eec13