Fix: Correct docker compose check in install script

[ShanSanear]

Proposed change

Adjusting the method of detecting the docker compose plugin to ensure that the script exits early if it is not installed.

Closes #5904

Type of change

• Bug fix: non-breaking change which fixes an issue.
• New feature / Enhancement: non-breaking change which adds functionality. Please read the important note above.
• Breaking change: fix or feature that would cause existing functionality to not work as expected.
• Documentation only.
• Other. Please explain:

Checklist:

• I have read & agree with the contributing guidelines.
• If applicable, I have included testing coverage for new code in this PR, for backend and / or front-end changes.
• If applicable, I have tested my code for new features & regressions on both mobile & desktop devices, using the latest version of major browsers.
• If applicable, I have checked that all tests pass, see documentation.
• I have run all pre-commit hooks, see documentation.
• I have made corresponding changes to the documentation as needed.
• I have checked my modifications for any breaking changes.

[paperless-ngx-secretary]

Hello @ShanSanear,

thank you very much for submitting this PR to us!

This is what will happen next:

1. My robotic colleagues will check your changes to see if they break anything. You can see the progress below.
2. Once that is finished, human contributors from paperless-ngx review your changes. Since this seems to be a small change, only a single contributor has to review your changes.
3. Please improve anything that comes up during the review until your pull request gets approved.
4. Your pull request will be merged into the dev branch. Changes there will be tested further.
5. Eventually, changes from you and other contributors will be merged into main and a new release will be made.

Please allow up to 7 days for an initial review. We're all very excited about new pull requests but we only do this as a hobby.
If any action will be required by you, please reply within a month.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.91%. Comparing base (d2f9b5d) to head (ebd6a69).

❗ Current head ebd6a69 differs from pull request most recent head fa0e028. Consider uploading reports for the commit fa0e028 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #5917      +/-   ##
==========================================
- Coverage   96.92%   96.91%   -0.02%     
==========================================
  Files         405      405              
  Lines       16197    16192       -5     
  Branches     1174     1175       +1     
==========================================
- Hits        15699    15692       -7     
- Misses        498      500       +2     

Flag	Coverage Δ
backend	95.59% <ø> (-0.03%)	⬇️
frontend	98.48% <ø> (ø)

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[github-actions]

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