doc: update BUILDING.md previous versions links

Remove links to End-of-Life versions of the BUILDING.md document.
Add a link to the version for Node.js 14.x.

PR-URL: #37082
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Beth Griggs <[email protected]>
Reviewed-By: Juan José Arboleda <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>

Author: richardlau

BUILDING.md

@@ -218,10 +218,9 @@ Supported platforms and toolchains change with each major version of Node.js.
 This document is only valid for the current major version of Node.js.
 Consult previous versions of this document for older versions of Node.js:
 
-* [Node.js 13](https://github.com/nodejs/node/blob/v13.x/BUILDING.md)
+* [Node.js 14](https://github.com/nodejs/node/blob/v14.x/BUILDING.md)
 * [Node.js 12](https://github.com/nodejs/node/blob/v12.x/BUILDING.md)
 * [Node.js 10](https://github.com/nodejs/node/blob/v10.x/BUILDING.md)
-* [Node.js 8](https://github.com/nodejs/node/blob/v8.x/BUILDING.md)
 
 ## Building Node.js on supported platforms