fix: use the right Go version in the CI (backport #346)

[mergify]

This is an automatic backport of pull request #346 done by Mergify.
Cherry-pick of 40e6fb3 has failed:

On branch mergify/bp/7.14/pr-346
Your branch is up to date with 'origin/7.14'.

You are currently cherry-picking commit 40e6fb3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .ci/Jenkinsfile

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of f888d11 has failed:

On branch mergify/bp/7.14/pr-346
Your branch is ahead of 'origin/7.14' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit f888d11.
  (all conflicts fixed: run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

nothing to commit, working tree clean

Cherry-pick of 078b9bc has failed:

On branch mergify/bp/7.14/pr-346
Your branch is ahead of 'origin/7.14' by 2 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 078b9bc.
  (all conflicts fixed: run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

nothing to commit, working tree clean

Cherry-pick of 0871589 has failed:

On branch mergify/bp/7.14/pr-346
Your branch is ahead of 'origin/7.14' by 3 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 0871589.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .ci/Jenkinsfile

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of 21328bf has failed:

On branch mergify/bp/7.14/pr-346
Your branch is ahead of 'origin/7.14' by 4 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 21328bf.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .ci/Jenkinsfile

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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