doc: Replace TP with Weblate mentions.

* doc/contributing.texi: Replace link to TP with a link to Weblate.
* doc/guix.texi: Replace link to TP with a link to Weblate.
* doc/guix-cookbook.texi: Replace link to TP with a link to Weblate.

doc/contributing.texi

@@ -593,8 +593,8 @@ such as @command{guix package --show} take care of rendering it
 appropriately.
 
 Synopses and descriptions are translated by volunteers
-@uref{https://translationproject.org/domain/guix-packages.html, at the
-Translation Project} so that as many users as possible can read them in
+@uref{https://translate.fedoraproject.org/projects/guix/packages, at
+Weblate} so that as many users as possible can read them in
 their native language.  User interfaces search them and display them in
 the language specified by the current locale.
 

doc/guix-cookbook.texi

@@ -57,8 +57,9 @@ its API, and related concepts.
 @c how to join your own translation team and how to report issues with the
 @c translation.
 If you would like to translate this document in your native language, consider
-joining the @uref{https://translationproject.org/domain/guix-cookbook.html,
-Translation Project}.
+joining
+@uref{https://translate.fedoraproject.org/projects/guix/documentation-cookbook,
+Weblate}.
 
 @menu
 * Scheme tutorials::            Meet your new favorite language!

doc/guix.texi

@@ -142,9 +142,9 @@ GNU Guix参考手册}), French (@pxref{Top,,, guix.fr, Manuel de référence de
 Guix}), German (@pxref{Top,,, guix.de, Referenzhandbuch zu GNU Guix}),
 Spanish (@pxref{Top,,, guix.es, Manual de referencia de GNU Guix}), and
 Russian (@pxref{Top,,, guix.ru, Руководство GNU Guix}).  If you
-would like to translate it in your native language, consider joining the
-@uref{https://translationproject.org/domain/guix-manual.html, Translation
-Project}.
+would like to translate it in your native language, consider joining
+@uref{https://translate.fedoraproject.org/projects/guix/documentation-manual,
+Weblate}.
 
 @menu
 * Introduction::                What is Guix about?