docs(changelog): correct the 0.82.0 fragments

[datlechin]

Why

Checked each 0.82.0 fragment against its PR's diff before the v0.82.0 notes are assembled. Six say more or less than the PR did, and two repeat or describe nothing a user sees.

Change

• feat(settings): get beta updates from a signed feed #3501: every update now comes from the signed feed, not only betas.
• build(native): read bridge toolchains from their pin files #3513: HANA 1.0.0 shipped the same unfixed Go helper as 1.0.1 to 1.0.3.
• feat(datagrid): generate UUIDs in Set Value and mark SQL functions #3446: the UUID functions left SQL Functions (changed.3 says so), ClickHouse today() was the other quoted function, ScyllaDB joins the Default list, and the SQLite half of fixed.7 is changed.6. fixed.8 repeats added.3, and the PluginKit ABI line names nothing a user sees.
• feat(settings): rebuild the theme system and theme every content surface #3452: 0.81 already synced the chosen light and dark themes; the files are new.

Verified

check-changelog.py and the banned-words check pass. Every PR on the line since v0.81.0 that a user would notice has a fragment.