clarify pipeline.md

[danistrebel]

Description

What's changed, or what was fixed?

• Clarify that the variables target both X and Edge

Fixes: #issue

Housekeeping

(please check all that apply [x], do not edit the text)

• [x] I have run all the tests locally and they all pass.
• [x] I have followed the relevant style guide for my changes.
• [ ] PR requires full pipeline run (Run for changes only by default).

CC: @apigee-devrel-reviewers

[danistrebel]

/gcbrun

[apigee-devrel-bot]

Pipeline Report

Pipeline	Result	Elapsed Wall Time
TOTAL PIPELINE (no change)	pass	0

View details in Cloud Build (permission required)

Commit version: 71d3c8b

[danistrebel]

Trivial PR. Using the force.