guix home: Default verbosity is the same as for 'guix system'.

Previously the default verbosity would always be 3, and
'verbosity-level' would thus have no effect.

* guix/scripts/home.scm (verbosity-level): Change to level 3 for
'build'.
(%default-options): Set 'verbosity' to #f.

guix/scripts/home.scm

@@ -105,7 +105,7 @@ Some ACTIONS support additional ARGS.\n"))
   "Return the verbosity level based on OPTS, the alist of parsed options."
   (or (assoc-ref opts 'verbosity)
       (if (eq? (assoc-ref opts 'action) 'build)
-          2 1)))
+          3 1)))
 
 (define %options
   ;; Specification of the command-line options.
@@ -137,7 +137,7 @@ Some ACTIONS support additional ARGS.\n"))
     (print-build-trace? . #t)
     (print-extended-build-trace? . #t)
     (multiplexed-build-output? . #t)
-    (verbosity . 3)
+    (verbosity . #f)                              ;default
     (debug . 0)))