profiles: Remove dead code.

* guix/profiles.scm (write-manifest): Remove.
  (read-manifest): Keep private.

guix/profiles.scm

@@ -45,9 +45,6 @@
             manifest-pattern
             manifest-pattern?
 
-            read-manifest
-            write-manifest
-
             manifest-remove
             manifest-installed?
             manifest-matching-entries
@@ -157,10 +154,6 @@
   "Return the packages listed in MANIFEST."
   (sexp->manifest (read port)))
 
-(define (write-manifest manifest port)
-  "Write MANIFEST to PORT."
-  (write (manifest->sexp manifest) port))
-
 (define (entry-predicate pattern)
   "Return a procedure that returns #t when passed a manifest entry that
 matches NAME/OUTPUT/VERSION.  OUTPUT and VERSION may be #f, in which case they