Bug 1509349 [wpt PR 14187] - Update interfaces/fetch.idl, a=testonly

Automatic update from web-platform-testsUpdate interfaces/fetch.idl (#14187)

Source: https://github.com/tidoust/reffy-reports/blob/ad6a3af/whatwg/idl/fetch.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/458282545
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wpt-commits: 53dc4fb61401f49e7312d1470139940b9892bb89
wpt-pr: 14187

testing/web-platform/tests/interfaces/fetch.idl

@@ -93,7 +93,7 @@ Response includes Body;
 
 dictionary ResponseInit {
   unsigned short status = 200;
-  ByteString statusText = "OK";
+  ByteString statusText = "";
   HeadersInit headers;
 };