docs: don't suffix page permalink with a slash

docs: don't suffix page permalink with a slash

As it breaks relative links to other pages. For example, the
BOOT_LOADER_INTERFACE page has a relative link to
AUTOMATIC_BOOT_ASSESSMENT. With a slash in the page's permalink, that
link leads to:

http://127.0.0.1:4000/BOOT_LOADER_INTERFACE/AUTOMATIC_BOOT_ASSESSMENT

which is incorrect. Dropping the trailing slash makes the link link to
the correct place:

http://127.0.0.1:4000/AUTOMATIC_BOOT_ASSESSMENT

Resolves: #32088