[stable32] do not re-install phpunit in integration ci

[grnd-alt]

ci for integration tests couldn't run before
comparison for a test run before: https://github.com/nextcloud/deck/actions/runs/22556727299/job/65335384451

phpunit is already installed in run.sh: https://github.com/nextcloud/server/blob/stable32/build/integration/run.sh#L41
so I don't know why this line would even be required tbh.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 83520 was 82773 (+0.9%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[grnd-alt]

/backport to stable31

[grnd-alt]

/backport to stable30

[backportbot]

The backport to stable31 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable31
git pull origin stable31

# Create the new backport branch
git checkout -b backport/7701/stable31

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick a157fea8

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/7701/stable31

Error: Failed to check for changes with origin/stable31: No changes found in backport branch

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[grnd-alt]

/backport to stable29