fix: replace hard coded go version reference with value from mod file

[anithapriyanatarajan]

Changes

This pull request updates the Go workflow configurations:

• Updated the actions/checkout step to use version v6.0.1 instead of v4.1.7 aligning to the ci workflow (https://github.com/tektoncd/chains/blob/main/.github/workflows/ci.yaml#L56)
• Changed the Go setup step to use the go-version-file option referencing go.mod, ensuring the workflow always uses the project's specified Go version instead of a hardcoded version.

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• Has Docs included if any changes are user facing
• Has Tests included if any functionality added or changed
• Follows the commit message standard
• Meets the Tekton contributor standards (including
  functionality, content, code)
• Release notes block below has been updated with any user facing changes (API changes, bug fixes, changes requiring upgrade notices or deprecation warnings)
• Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

NONE

/kind misc

[tekton-robot]

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