Fix: backend time conversion of fixed timeouts

[zwilling]

Description

Fixed timeouts did not work. There was a small scope mistake in the calculation of the expiration time. It converted contributionStartedAt from minutes to millis although contributionStartedAt already was in millis.

How Has This Been Tested?

• Deployment finished without errors
• Running the unittests yarn test:prod
• Completing the Galactica Network Ceremony

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (Is there something to change?)
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• I reviewed the code of conduct and contributors' guide