Bug 1571620 [wpt PR 18289] - Update interfaces/speech-api.idl, a=test…

…only

Automatic update from web-platform-tests
Update interfaces/speech-api.idl (#18289)

Source: https://github.com/tidoust/reffy-reports/blob/acde19a/whatwg/idl/speech-api.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/568218224
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wpt-commits: 5ba486c2f31886e43f8b55ba6ca0ebea67afe18d
wpt-pr: 18289

testing/web-platform/tests/interfaces/speech-api.idl

@@ -90,7 +90,7 @@ dictionary SpeechRecognitionEventInit : EventInit {
 };
 
 // The object representing a speech grammar
-[Exposed=Window, Constructor]
+[Exposed=Window]
 interface SpeechGrammar {
     attribute DOMString src;
     attribute float weight;