[DOCS] Fix footer, banner, TOC, EMR doc, Databricks doc

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read Contributor Rules and Contributor Development Guide

Is this PR related to a JIRA ticket?

• No, this is a documentation update. The PR name follows the format [DOCS] my subject.

What changes were proposed in this PR?

• Remove a part of the customized template. This fixed
  • The ugly footer
  • Wrong name of the Table of Content
• Update the banner to show latest stable version
• Fixed the broken discord link
• Updated the EMR doc to warn the sedona version
• Updated the Databricks doc to warn the sedona version

How was this patch tested?

LGTM locally

Did this PR include necessary documentation updates?

• Yes, I have updated the documentation update.