Replace docker-compose with docker compose

[cmurphy]

Fixes CI error "ERROR: for rekor_rekor-server_1 'ContainerConfig'".

See https://forums.docker.com/t/docker-compose-up-fails-after-yesterday-update-possible-regression-in-2-25-0-1/140430/9

Summary

Release Note

Documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.28%. Comparing base (488eb97) to head (299cae3).
Report is 137 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2153       +/-   ##
===========================================
- Coverage   66.46%   50.28%   -16.18%     
===========================================
  Files          92       92               
  Lines        9258     7308     -1950     
===========================================
- Hits         6153     3675     -2478     
- Misses       2359     2760      +401     
- Partials      746      873      +127     

Flag	Coverage Δ
e2etests	50.28% <ø> (+2.72%)	⬆️
unittests	?

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[bobcallaway]

I used a conditional for environments who haven't updated to the latest version of docker in

rekor/e2e-test.sh

Line 20 in 332c7ca

docker_compose="docker compose -f docker-compose.yml -f docker-compose.test.yml"

- you might want to do something similar here

[cmurphy]

@bobcallaway done