Remove use of etc and time gems in Puma

[MSP-Greg]

Description

Several years ago the etc and time gems were added to Puma's requirements. They are no longer needed, as a small code change replaces time, and I can't find any reference to etc.

Closes #3033.

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[MSP-Greg]

@nateberkopec bug, refactor, or feature ?

[johnnyshields]

LGTM