docs: clean up unreleased changelog section for v3.0.0 #519

Job	Run time
Code checks / Actions lint check	31s
Tests / Integration tests (3.11, ubuntu-latest)	2m 28s
Code checks / Spell check	6s
Docstrings checks / Docstrings checks	13s
Tests / Integration tests (3.14, ubuntu-latest)	2m 18s
PR title check	3s
Code checks / Lint check / Lint check (3.11)	12s
Code checks / Lint check / Lint check (3.14)	10s
Code checks / Type check / Type check (3.13)	11s
Code checks / Type check / Type check (3.11)	12s
Code checks / Lint check / Lint check (3.13)	11s
Code checks / Type check / Type check (3.12)	13s
Code checks / Lint check / Lint check (3.12)	12s
Code checks / Type check / Type check (3.14)	13s
Doc checks / Doc checks / Docs check	1m 20s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.13)	44s
Tests / Unit tests / Unit tests (windows-latest, 3.11)	56s
Tests / Unit tests / Unit tests (windows-latest, 3.14)	59s
Tests / Unit tests / Unit tests (windows-latest, 3.12)	1m 8s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.12)	43s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.14)	38s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.11)	41s
Tests / Unit tests / Unit tests (windows-latest, 3.13)	1m 10s
	15m 32s

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