Use the Do Not Track parameter in vimeo videos

With this parameter, Vimeo no longer uses cookies that identifies users
browsing our site.

They do still store some cookies, though; quoting from Vimeo player
parameters overview:

> When DNT is enabled, Vimeo deploys one essential cookie via the
> embeddable player:
> The __cf_bm cookie, which is part of Cloudflare's Bot Management
> service and helps mitigate risk associated with spam and bot traffic.

Not sure whether this counts as essential cookies in our case; they're
essential for Vimeo, but for us, they're third-party cookies, after all.

[1] https://help.vimeo.com/hc/en-us/articles/12426260232977-Player-parameters-overview

app/components/shared/embedded_video_component.rb

@@ -43,9 +43,9 @@ class Shared::EmbeddedVideoComponent < ApplicationComponent
 
     def src
       if server == "Vimeo"
-        "https://player.vimeo.com/video/"
+        "https://player.vimeo.com/video/#{match[2]}?dnt=1"
       elsif server == "YouTube"
-        "https://www.youtube-nocookie.com/embed/"
+        "https://www.youtube-nocookie.com/embed/#{match[2]}"
       end
     end
 
@@ -54,6 +54,6 @@ class Shared::EmbeddedVideoComponent < ApplicationComponent
     end
 
     def iframe_attributes
-      tag.attributes(src: "#{src}#{match[2]}", style: "border:0;", allowfullscreen: true, title: title)
+      tag.attributes(src: src, style: "border:0;", allowfullscreen: true, title: title)
     end
 end