Update modus-themes to version 1.4.0

Update modus-themes to version 1.4.0

* doc/misc/modus-themes.org:
(Overview): Document good support for cases with red-green color
deficiency (deuteranopia).
(Customization Options): Add code block with sample configuration.
(Option for mode line presentation): Document new values.
(Option for completion framework aesthetics): Reword statements.
(Option for mail citations): Include new customization.
(Option for line highlighting (hl-line-mode)): Change description
of possible value.
(Option for diff buffer looks): Update the meaning of 'fg-only',
which now is an alias for 'fg-only-deuteranopia'.
(Option for org-mode block styles): Rename possible values.
(Cycle through arbitrary colors (DIY)): Include code samples for
demo case.
(Override colors (DIY)): Use correct symbol.
(Override color saturation (DIY)): Show how to combine manual and
automatic color overrides.
(Update Org block delimiter fontification (DIY)): Provide example.
(Load theme depending on time of day): Include missing "DIY" label.
(Full support for packages or face groups): Update list with
additions, removals.
(Indirectly covered packages): Update list.
(Notes for individual packages)
(Note on dimmer.el)
(Note on display-fill-column-indicator-mode)
(Note on mmm-mode.el background colors)
(Note on prism.el)
(Note on ERC escaped color sequences)
(Note on powerline or spaceline)
(Note on Helm grep)
(Note on EWW and Elfeed fonts (SHR fonts)): Stylistic change to
the heading.
(Note on inline Latex in Org buffers)
(Note on god-mode.el): Add note.
(Frequently Asked Questions (FAQ)): Include new section.
(Acknowledgements): Update list of contributors (bug#48647).
* etc/themes/modus-operandi-theme.el: Bump version number.

* etc/themes/modus-themes.el: Add new defcustom forms and update
existing ones, edit doc strings, remove old obsolete aliases,
tweak internal functions, refine face specifications.

* etc/themes/modus-vivendi-theme.el: Bump version number.