Update set-up-app-links.md

[AbdellatifAmireh]

add space between the sha256_cert_fingerprints

Description of what this PR is changing or adding, and why:

Issues fixed by this PR (if any):

PRs or commits this PR depends on (if any):

Presubmit checklist

• This PR is marked as draft with an explanation if not meant to land until a future stable release.
• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[google-cla]

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[parlough]

Thanks for the PR! However, we won't be able to review your PR until you sign the CLA as the earlier comment outlines.

If you have any issues doing so, let us know. Thanks again :)