chore(build): workaround set-env deprecation

[sfoster1]

Github recently disabled the ::set-env command in their protocol runners because it was insecure (https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/). The fix for this was to use environment file piping instead. Unfortunately, even if you're interacting with it through e.g. a node wrapper like in https://github.com/actions/core, this is what you're always doing, so core needed a bump to v1.2.6 in all its dependencies. This didn't happen in https://github.com/actions/github-script as of this writing (open pr: actions/github-script#91) and therefore our builds started breaking.

The workaround is to enable the old behavior and have a message that yells at you about it.

[codecov]

Codecov Report

Merging #7010 (8935e01) into chore_release-4.0.0-beta.0 (c382681) will decrease coverage by 3.90%.
The diff coverage is n/a.

@@                      Coverage Diff                       @@
##           chore_release-4.0.0-beta.0    #7010      +/-   ##
==============================================================
- Coverage                       73.23%   69.33%   -3.91%     
==============================================================
  Files                             263      147     -116     
  Lines                           21107    15722    -5385     
==============================================================
- Hits                            15458    10901    -4557     
+ Misses                           5649     4821     -828     

Impacted Files	Coverage Δ
...er/robot_server/service/json_api/resource_links.py
update-server/otupdate/buildroot/config.py
notify-server/notify_server/clients/queue_entry.py
...rver/robot_server/service/session/configuration.py
...er/robot_server/service/legacy/routers/pipettes.py
.../robot_server/robot/calibration/check/user_flow.py
.../session/session_types/deck_calibration_session.py
...r/robot_server/robot/calibration/deck/dev_types.py
update-server/otupdate/buildroot/update.py
...bot-server/robot_server/service/json_api/errors.py
... and 106 more

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[mcous]

LGTM