scripts: Use translations for guix.pot for service descriptions.

Previously, service descriptions appeared in both guix.pot and
packages.pot, but only translations of packages.pot were used.
Now, translations are only done with guix.pot.

This is better, because translators are more likely to translate
guix.pot, and is also easier, because files in gnu/{home/,}services
need to be in po/guix/POTFILES.in anyway and po/guix/Makevars
already acts on the 'description' keyword because of lint checkers.

* guix/scripts/home.scm (service-type-description-string):
Use translations from guix.pot.
* guix/scripts/system/search.scm (service-type-description-string)
(service-type->recutils): Likewise.
* po/packages/POTFILES.in: Move files in gnu/services to ...
* po/guix/POTFILES.in: ... here.

guix/scripts/home.scm

@@ -705,7 +705,7 @@ deploy the home environment described by these files.\n")
 (define (service-type-description-string type)
   "Return the rendered and localised description of TYPE, a service type."
   (and=> (service-type-description type)
-         (compose texi->plain-text P_)))
+         (compose texi->plain-text G_)))
 
 (define %service-type-metrics
   ;; Metrics used to estimate the relevance of a search result.

guix/scripts/system/search.scm

@@ -127,7 +127,7 @@ procedure that may return a colorized version of its argument."
                (parameterize ((%text-width width*))
                  (texi->plain-text
                   (string-append "description: "
-                                 (or (and=> (service-type-description type) P_)
+                                 (or (and=> (service-type-description type) G_)
                                      ""))))
                #\newline)))))
 
@@ -144,7 +144,7 @@ procedure that may return a colorized version of its argument."
 (define (service-type-description-string type)
   "Return the rendered and localised description of TYPE, a service type."
   (and=> (service-type-description type)
-         (compose texi->plain-text P_)))
+         (compose texi->plain-text G_)))
 
 (define %service-type-metrics
   ;; Metrics used to estimate the relevance of a search result.

po/guix/POTFILES.in

@@ -4,10 +4,14 @@ gnu.scm
 gnu/packages.scm
 gnu/services.scm
 gnu/system.scm
+gnu/services/base.scm
+gnu/services/certbot.scm
 gnu/services/configuration.scm
+gnu/services/file-sharing.scm
 gnu/services/networking.scm
 gnu/services/shepherd.scm
 gnu/services/samba.scm
+gnu/services/version-control.scm
 gnu/home/services.scm
 gnu/home/services/ssh.scm
 gnu/home/services/symlink-manager.scm

po/packages/POTFILES.in

@@ -57,8 +57,3 @@ gnu/packages/webkit.scm
 gnu/packages/web.scm
 gnu/packages/wordnet.scm
 gnu/packages/xiph.scm
-gnu/services/base.scm
-gnu/services/certbot.scm
-gnu/services/file-sharing.scm
-gnu/services/networking.scm
-gnu/services/version-control.scm