documentation: add comment to releases.rst switchers.js

To let release developers know that they don't need
to update these files in release branches other than "master".

(From yocto-docs rev: 00f71afae92e5967a0422824841d4d4db682d235)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/sphinx-static/switchers.js

@@ -1,3 +1,11 @@
+/*
+NOTE FOR RELEASE MAINTAINERS:
+This file only needs updating in the development release ("master" branch)
+When documentation for stable releases is built,
+the latest version from "master" is used
+by https://git.yoctoproject.org/yocto-autobuilder-helper/tree/scripts/run-docs-build
+*/
+
 (function() {
   'use strict';