docs: update link to APM server 7.0 upgrade guide

[jrodewig]

Updates a link to the APM Server 7.0 upgrade guide. This link doesn't exist in 8.0+ and will break when we release 8.0 GA.

NOTE: The link currently directs users to 7.17 so we may want to wait until after the 7.17 release before merging.

We'll also need to backport to 5.x.

Relates to elastic/docs#2312

Preview

https://apm-agent-rum-js_1153.docs-preview.app.elstc.co/guide/en/apm/agent/rum-js/master/upgrade-to-v5.html#v5-upgrade-server

[apmmachine]

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• Reason: null

• Start Time: 2022-01-28T13:34:47.062+0000

• Duration: 17 min 19 sec

• Commit: 24f5742

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[ollyhowell]

LGTM!

[devcorpio]

Hi @jrodewig

you may need to change the message of each of your commits to this format docs: <msg> to pass the Lint check. (You may need to update the PR title too)

[jrodewig]

Thanks for the pointer, @devcorpio!

[apmmachine]

📦 Bundlesize report

Filename	Size(bundled)	Size(gzip)	Diff(gzip)
elastic-apm-opentracing.umd.min.js	63.8 KiB	20.3 KiB	💚 0 Bytes
elastic-apm-rum.umd.min.js	57.7 KiB	18.8 KiB	💚 0 Bytes

[jrodewig]

@bmorelli25 Do you mind merging and backporting this to 5.x when convenient?

I'd do it myself, but I lack the permissions. ☹️

Thanks!

[bmorelli25]

Yup! Thanks, James!