docs: add missing password manager removal to changelog

[ThomasFrans]

As this is a breaking change, it should definitely be represented in the changelog, which is the primary source of information about any user-facing changes.

Describe your changes

Add the removal of the password manager feature to the "Removed" section of the changelog.
Also update the wording for another item in the "Fixed" section to say exactly what was fixed.

Issue ticket number and link

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Checklist before requesting a review

• Documentation was updated (i.e. due to changes in keybindings, commands, etc.)
• Changelog was updated with relevant user-facing changes (eg. not dependency updates,
  not performance improvements, etc.)

(I'll also create a separate PR to remove some remaining documentation about the password manager feature.)

[hrkfdn]

Makes sense, thank you!