Move version support table to Upcoming Releases

This change helps guarantee that we'll update the version support table
at the same time as the upcoming release table to keep our support
windows up to date. Since we otherwise do not update the two tables at
the same time, the supported version table has become out of date.

This change also updates support windows based on the plan to release
v18 in May, 2025, with the assumption that we release a major version
every 4 months.

This change also moves the compatibility description from FAQ to
Upcoming Releases so we keep this info in one place, and links to
Upcoming Releases from the relevant section of the FAQ.

Author: ptgott

docs/pages/faq.mdx

@@ -93,24 +93,8 @@ time you run `tsh`.
 
 ## Which version of Teleport is supported?
 
-Teleport releases a new major version approximately every 4 months, and provides
-security-critical support for the current and two previous major versions. With
-our typical release cadence, we usually support each major version for 12
-months.
-
-### Supported versions
-
-Here are the major versions of Teleport and their support windows:
-
-| Release | Release Date      | EOL           | Minimum `tsh` version |
-|---------|-------------------|---------------|-----------------------|
-| v17.0   | November 16, 2024 | November 2025 | v16.0.0               |
-| v16.0   | June 14, 2024     | June 2025     | v15.0.0               |
-| v15.0   | January 29, 2024  | January 2025  | v14.0.0               |
-
-### Version compatibility
-
-(!docs/pages/includes/compatibility.mdx!)
+See [Upcoming Releases](upcoming-releases.mdx) for the versions of Teleport that
+we support and how long we plan to continue supporting them.
 
 ## Does the Web UI support copy and paste?
 

docs/pages/upcoming-releases.mdx

@@ -3,16 +3,29 @@ title: Teleport Upcoming Releases
 description: A timeline of upcoming Teleport releases.
 ---
 
-The Teleport team delivers a new major release roughly every 4 months.
+Teleport releases a new major version approximately every 4 months, and provides
+security-critical support for the current and two previous major versions. With
+our typical release cadence, we usually support each major version for 12
+months.
 
 ## Teleport
 
+We plan to release the following versions in the coming months:
+
 | Version | Date                        |
 |---------|-----------------------------|
 | 17.4.0  | Week of March 24th, 2025    |
 | 17.5.0  | Week of May 19th, 2025      |
 | 18.0.0  | Week of May 26th, 2025      |
 
+We continue to support the following major versions of Teleport:
+
+| Release | Release Date      | EOL            | Minimum `tsh` version |
+|---------|-------------------|----------------|-----------------------|
+| v17.x   | November 16, 2024 | January 2026   | v16.0.0               |
+| v16.x   | June 14, 2024     | September 2025 | v15.0.0               |
+| v15.x   | January 29, 2024  | May 2025       | v14.0.0               |
+
 ### 17.4.0
 
 #### Database access for Oracle RDS
@@ -117,3 +130,8 @@ minor release, such as (=teleport.major_version=).1.0.
 
 Patch releases contain small bug fixes and can typically be deployed directly
 to production.
+
+## Version compatibility
+
+(!docs/pages/includes/compatibility.mdx!)
+