DOCS-28 - Grok deprecation

[jpipkin1]

Purpose of this pull request

This pull request adds an article that is only available to those who have the link: https://help.sumologic.com/docs/cse/schema/grok-deprecation-notice

Ticket

https://sumologic.atlassian.net/browse/DOCS-28

(Created from Asana ticket "Grok deprecation notice")

Select the type of change:

• [ ] Minor Changes - Typos, formatting, slight revisions, .clabot
• [ ] Update Content - Revisions, updating sections
• [x] New Content - New features, sections, pages, tutorials
• [ ] Site and Tools - Updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

PLEASE READ

Following a recent back-end update, all contributors with a local clone or fork of our repository are required to run yarn install. This does not apply to direct page edits.

• [x] Yes, I've run yarn install
• [ ] No, does not apply to me

[jpipkin1]

This PR is in draft until the deprecation notice is finalized.