Update modus-themes to their version 2.5.0

Update modus-themes to their version 2.5.0

* doc/misc/modus-themes.org (Debian 11 Bullseye): Clarify that the
Debian package as it is long outdated.
(Option for inhibiting theme reload): Fix typo
(Option for completion framework aesthetics): Remove reference to
obsolete package.
(Option for line highlighting): Mention 'lin' package from GNU ELPA.
(Option for the headings' overall style): Document support for
headings level 0.
(Advanced customization): Fix typo.
(Override colors): Remove obsolete entries.  Add link to new section.
(Override colors through blending): Add section with a complete
technology demonstration of overriding the color values.
(Font configurations for Org and others): Mention the 'fontaine'
package from GNU ELPA.
(Custom Org emphasis faces): Fix typo.
(Full support for packages or face groups, Indirectly covered
packages): Update list of supported packages.
(Note on vc-annotate-background-mode): Remove note.:(Are these color
schemes?): Fix typo.
(Acknowledgements): Update acknowledgements.
* etc/themes/modus-operandi-theme.el
* etc/themes/modus-vivendi-theme.el: Update version header.

* etc/themes/modus-themes.el (modus-themes--version): Update version.
(modus-themes-special-cold, modus-themes-special-mild)
(modus-themes-special-warm, modus-themes-special-calm)
(modus-themes-diff-added, modus-themes-diff-changed)
(modus-themes-diff-removed, modus-themes-diff-refine-added)
(modus-themes-diff-refine-changed, modus-themes-diff-refine-removed)
(modus-themes-diff-focus-added, modus-themes-diff-focus-changed)
(modus-themes-diff-focus-removed, modus-themes-mark-symbol)
(modus-themes-inhibit-reload, modus-themes-mode-line)
(modus-themes--paren): Fix doc string warning about quotes.
(modus-themes-operandi-color-overrides)
(modus-themes-vivendi-color-overrides): Fix ":link" to the Info
manual's relevant node.
(modus-themes-headings): Add support for headings level 0.
(modus-themes-org-agenda): Tweak spacing in the doc string.
(modus-themes--syntax-comment): Tweak combination of properties.
(modus-themes--list-colors-render, modus-themes-list-colors): Refine
how the command works to preview colors in the buffer.
(modus-themes-faces): Edit supported faces.
(modus-themes-custom-variables): Edit supported variables.

Release notes: <https://protesilaos.com/codelog/2022-08-03-modus-themes-2-5-0/>.