[tests] Fix timezone dependency

[yumkam]

Not visible on CI (or other machines with TZ=UTC)

Changelog entry

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Changelog category

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Description for reviewers

Have not used "...Z" to remain compatible with python3 < 3.11

[github-actions]

🟢 2025-02-25 15:11:11 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-02-25 15:09:12 UTC Pre-commit check linux-x86_64-release-asan for 05debc1 has started.
⚪ 2025-02-25 15:09:40 UTC Artifacts will be uploaded here
⚪ 2025-02-25 15:12:39 UTC ya make is running...
🟢 2025-02-25 15:14:20 UTC Tests successful.

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
24	24	0	0	0	0

🟢 2025-02-25 15:14:30 UTC Build successful.
🟢 2025-02-25 15:14:44 UTC ydbd size 3.6 GiB changed* by +52.4 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 9029d02	merge: 05debc1	diff	diff %
ydbd size	3 900 116 896 Bytes	3 900 170 512 Bytes	+52.4 KiB	+0.001%
ydbd stripped size	1 365 335 376 Bytes	1 365 352 272 Bytes	+16.5 KiB	+0.001%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[github-actions]

⚪ 2025-02-25 15:11:56 UTC Pre-commit check linux-x86_64-relwithdebinfo for 05debc1 has started.
⚪ 2025-02-25 15:12:11 UTC Artifacts will be uploaded here
⚪ 2025-02-25 15:14:32 UTC ya make is running...
🟢 2025-02-25 15:21:57 UTC Tests successful.

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
874	865	0	0	9	0

🟢 2025-02-25 15:22:16 UTC Build successful.
🟢 2025-02-25 15:22:25 UTC ydbd size 2.1 GiB changed* by +29.3 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 9029d02	merge: 05debc1	diff	diff %
ydbd size	2 243 209 832 Bytes	2 243 239 880 Bytes	+29.3 KiB	+0.001%
ydbd stripped size	474 901 528 Bytes	474 910 200 Bytes	+8.5 KiB	+0.002%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}