Correct Cookie doc link

The existing link points to https://github.com/varnish/varnish-modules/blob/master/docs/cookie.rst
and the working link is https://github.com/varnish/varnish-modules/blob/master/docs/vmod_cookie.rst.

R1/source/vmods/vmod_cookie.json

@@ -5,7 +5,7 @@
         "branches": {
             "4.1": "master"
         },
-        "doc_path": "docs/cookie.rst",
+        "doc_path": "docs/vmod_cookie.rst",
         "project": "varnish-modules",
         "user": "varnish",
         "vcc_path": "src/vmod_cookie.vcc"
@@ -16,4 +16,4 @@
     "support": [
         "Varnish Software"
     ]
-}
\ No newline at end of file
+}