gnu: emacs-json-mode: Update to 1.0.15.

* gnu/packages/emacs-xyz.scm (emacs-json-mode): Update to 1.0.15.
[source]<origin>: Use ".tar" extension, since ".el" is only possible for first
release ever in GNU ELPA.

gnu/packages/emacs-xyz.scm

@@ -14686,14 +14686,14 @@ highlighting.")
 (define-public emacs-jsonrpc
   (package
     (name "emacs-jsonrpc")
-    (version "1.0.14")
+    (version "1.0.15")
     (source
      (origin
        (method url-fetch)
        (uri (string-append "https://elpa.gnu.org/packages/"
-                           "jsonrpc-" version ".el"))
+                           "jsonrpc-" version ".tar"))
        (sha256
-        (base32 "069l0sqkambam4ikj9id36kdw1jdjna8v586d51m64hiz96rmvm6"))))
+        (base32 "1hx378rg12jz2zm105cvrqk0nqyzsn04l59d903l98d6lbd96rsw"))))
     (build-system emacs-build-system)
     (home-page "http://elpa.gnu.org/packages/jsonrpc.html")
     (synopsis "JSON-RPC library")