Update dependency tzdata to v2026.3

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
tzdata	==2026.2 → ==2026.3

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Release Notes

python/tzdata (tzdata)

v2026.3: : Release of upstream tzdata 2026c

Compare Source

Version 2026.3

Upstream version 2026c released 2026-07-08T17:23:58+00:00

Briefly:

Alberta moved to permanent -06 on 2026-06-18. Morocco moves to permanent +00 on
2026-09-20. More integer overflow bugs have been fixed in zic.

Changes to future timestamps

Alberta’s 2026-03-08 spring forward was its last foreseeable clock change, as it
moved to permanent -06 thereafter. (Thanks to Roozbeh Pournader and others.)
Model this with its traditional abbreviation CST. Although the change to
permanent -06 legally took place on 2026-06-18, temporarily model the change to
occur on 2026-11-01 at 02:00 instead, for the same reason we introduced a
similarly temporary hack for British Columbia in 2026b.

Although another TZDB release will likely be needed soon because Northwest
Territories will likely follow Alberta, the legal formalities have not yet taken
place.

Morocco plans to move back to permanent UTC, without daylight saving time
transitions, on 2026-09-20 at 02:00. This also affects Western Sahara.

Changes to commentary

Northwest Territories is expected to move to permanent -06 prior to 2026-11-01
02:00, when clocks would otherwise fall back. (Thanks to Tim Parenti and James
Bellaire.) Model this with its traditional abbreviation CST. Unfortunately the
change is not yet official, so it is currently present only as comments that can
be uncommented as needed.

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