docs (java-firestore): Broken redirects, samples and reference links in the README

[zeroNhatty]

The java-firestore/README.md contains multiple broken reference links.

Broken Elements

1. Client Library Documentation: Points to the client library history.

   • Expected: Should point to https://cloud.google.com/java/docs/reference/google-cloud-firestore ( or the /latest/overview landing page).
   • Locations: Found in the first section of the README and under the section called About Cloud Firestore.

2. Authentication: Points to a non-existent anchor tag in the repository root README.

   • Location: Found under the Authentication Section.

3. Samples: The most severely broken links are found here. The main link for samples/ points to a non-existent directory. Additionally, inside the table, all source code links point to non-existent destinations as well possibly because they are missing the java-firestore/ subdirectory context.

   • Location: Found under the Samples section.

4. shared Troubleshooting document: Points to a non-existent destination at the root level.

   • Location: Found under the Troubleshooting section.