DP-9030: Fix a typo in withGradleFile causing failed builds

[vinnybod]

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This is a follow up to the previous pull request to convert the Jenkinsfile to using withGradleFile.
It looks like when it was cherry-picked to 2.4 and 2.5, it was incorrectly merged and uses [[ ]] instead of [ ].
Once this is merged, it only needs to be cherry-picked to 2.5. The rest of the release branches are correct.

Summary of testing strategy (including rationale)
for the feature or bug fix. Unit and/or integration
tests are expected for any behaviour change and
system tests should be considered for larger changes.

I tested this using a replay on 2.4 in Jenkins. The build is green.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[vinnybod]

Looks like this passed, but there's an issue with the downstream check job actually returning back a success. I checked the log and it says "PASSED".