gnu: tzdata-for-tests: Update to 2018g.

* gnu/packages/base.scm (tzdata-for-tests): Inherit TZDATA.

gnu/packages/base.scm

@@ -1173,23 +1173,7 @@ and daylight-saving rules.")
 (define-public tzdata-for-tests
   (hidden-package
    (package
-     (inherit tzdata)
-     (version "2018d")
-     (source (origin
-               (method url-fetch)
-               (uri (string-append "https://www.iana.org/time-zones/repository"
-                                   "/releases/tzdata" version ".tar.gz"))
-               (sha256
-                (base32
-                 "0m6020dnk9r40z7k36jp13fa06xip3hn0fdx3nly66jzxgffs1ji"))))
-     (inputs `(("tzcode" ,(origin
-                            (method url-fetch)
-                            (uri (string-append
-                                  "http://www.iana.org/time-zones/repository/releases/tzcode"
-                                  version ".tar.gz"))
-                            (sha256
-                             (base32
-                              "1nd882yhsazmcfqmcqyfig3axycryl30gmizgqhqsx5dpa2lxr3x")))))))))
+     (inherit tzdata))))
 
 (define-public libiconv
   (package