[2.x] docs: update moved secret token link

[bmorelli25]

For elastic/apm-server#2728. Must be merged at the same time.

[vigneshshanmugam]

Do we need to backport docs changes to previous versions?

[bmorelli25]

@vigneshshanmugam In this case yes. We've restructured the APM Server documentation drastically (which we typically don't do) and it caused the destination of the secret token link to move pages (elastic/apm-server#2728 (comment)). I have to fix the link as far back as it exists in the RUM documentation.

You are correct that typically this wouldn't be needed as I don't move links around that often.

ci/docs failure is expected as elastic/apm-server#2728 hasn't been merged yet.

[vigneshshanmugam]

@bmorelli25 Thanks for the detailed info 🙂. Do you want to wait for the serer PR to get merged before merging this change?

The changes looks good to me.

[bmorelli25]

It's a weird one because if I merge any of these without the others, it will break the main doc build. I'm going to wait for ci to be green (except for docs) and merge all 5 PRs at the same time.

[vigneshshanmugam]

Haha, you need a merge bot now 😄