chore: fix typo in script in the getting started guide

[gckopper]

Changes

Adding missing 'u' from the word squashfs in the script responsible for downloading the kernel and rootfs

Reason

This is clearly a typo and, although it doesn't break the script, leads to names like 'ubuntu-.ext4' instead of 'ubuntu-24.04.ext4' which are not very helpful.

License Acceptance

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CONTRIBUTING.md.

PR Checklist

• I have read and understand CONTRIBUTING.md.
• I have run tools/devtool checkstyle to verify that the PR passes the
  automated style checks.
• I have described what is done in these changes, why they are needed, and
  how they are solving the problem in a clear and encompassing way.
• I have updated any relevant documentation (both in code and in the docs)
  in the PR.
• I have mentioned all user-facing changes in CHANGELOG.md.
• If a specific issue led to this PR, this PR closes the issue.
• When making API changes, I have followed the
  Runbook for Firecracker API changes.
• I have tested all new and changed functionalities in unit tests and/or
  integration tests.
• I have linked an issue to every new TODO.

---

• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.90%. Comparing base (266599a) to head (6bdf64b).
Report is 1 commits behind head on main.

❗ Current head 6bdf64b differs from pull request most recent head eff6fd3

Please upload reports for the commit eff6fd3 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5255      +/-   ##
==========================================
+ Coverage   82.84%   82.90%   +0.05%     
==========================================
  Files         250      250              
  Lines       26967    26967              
==========================================
+ Hits        22342    22356      +14     
+ Misses       4625     4611      -14     

Flag	Coverage Δ
5.10-c5n.metal	83.33% <ø> (ø)
5.10-m5n.metal	83.33% <ø> (+<0.01%)	⬆️
5.10-m6a.metal	82.54% <ø> (-0.01%)	⬇️
5.10-m6g.metal	?
5.10-m6i.metal	83.32% <ø> (ø)
5.10-m7a.metal-48xl	82.54% <ø> (?)
5.10-m7g.metal	79.16% <ø> (ø)
5.10-m7i.metal-24xl	83.28% <ø> (?)
5.10-m7i.metal-48xl	83.29% <ø> (?)
5.10-m8g.metal-24xl	79.16% <ø> (?)
5.10-m8g.metal-48xl	79.16% <ø> (?)
6.1-c5n.metal	83.38% <ø> (ø)
6.1-m5n.metal	83.37% <ø> (ø)
6.1-m6a.metal	82.59% <ø> (ø)
6.1-m6g.metal	79.16% <ø> (ø)
6.1-m6i.metal	83.37% <ø> (ø)
6.1-m7g.metal	79.16% <ø> (ø)
6.1-m7i.metal-24xl	83.38% <ø> (?)
6.1-m7i.metal-48xl	83.38% <ø> (?)
6.1-m8g.metal-24xl	79.16% <ø> (?)
6.1-m8g.metal-48xl	79.16% <ø> (?)

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[ShadowCurse]

Hi @gckopper, can you add a body to the commit message? Otherwise our CI complains.