chore: fixed code logic (timezones 🤷)

[fearphage]

This test fails consistently locally. There seems to be a logic issue with respect to time zones.

Details

The test expects to run on midnight Tuesday UTC (2022-06-28) using a fake timer. However it was actually generating a date that was relative to the local time. So for me, midnight UTC is 7pm CDT on the previous day (06-27 which is a Monday) so the test would fail. I patched this by always adjusting the time based on the timezone offset.

Verification

From a very basic set of local testing, it seems to pass consistently (where the main branch fails):

➜  backstage-actions git:(cron/fix-test) for x in America/Los_Angeles America/New_York Etc/GMT Africa/Nairobi Asia/Tokyo Pacific/Kiritimati; do if env TZ="$x" yarn test cron/mergeRenovatePRs.test.ts &> /dev/null; then outcome='passed'; else outcome='FAILED'; fi; printf '%-20s -> %s\n' "$x" "$outcome"; done
America/Los_Angeles  -> passed
America/New_York     -> passed
Etc/GMT              -> passed
Africa/Nairobi       -> passed
Asia/Tokyo           -> passed
Pacific/Kiritimati   -> passed
➜  backstage-actions git:(cron/fix-test) gcm
Switched to branch 'main'
Your branch is up to date with 'origin/main'.
➜  backstage-actions git:(main) for x in America/Los_Angeles America/New_York Etc/GMT Africa/Nairobi Asia/Tokyo Pacific/Kiritimati; do if env TZ="$x" yarn test cron/mergeRenovatePRs.test.ts &> /dev/null; then outcome='passed'; else outcome='FAILED'; fi; printf '%-20s -> %s\n' "$x" "$outcome"; done
America/Los_Angeles  -> FAILED
America/New_York     -> FAILED
Etc/GMT              -> passed
Africa/Nairobi       -> passed
Asia/Tokyo           -> passed
Pacific/Kiritimati   -> passed

EDIT: I originally thought the test was bad, but the code was actually flawed. So I just fixed that instead.