Cherry-pick (#13988): correct legacy config filename

[aparajit-pratap]

Purpose

Cherry-pick (#13988): correct legacy config filename

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated
• This PR contains no files larger than 50 MB

Release Notes

(FILL ME IN) Brief description of the fix / enhancement. Mandatory section

Reviewers

(FILL ME IN) Reviewer 1 (If possible, assign the Reviewer for the PR)

(FILL ME IN, optional) Any additional notes to reviewers or testers.

FYIs

(FILL ME IN, Optional) Names of anyone else you wish to be notified of