Removed blink flag for charLength in SpeechSynthesisEvent

Intent to ship discussion on blink-dev: https://groups.google.com/a/chromium.org/forum/?utm_medium=email&utm_source=footer#!msg/blink-dev/wXbIl5mq4eo/GSyt-hXeBQAJ

Bug: 923556
Change-Id: I805175cff562fe127a674b079023ff7dbc8ed32b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1627697
Commit-Queue: Samuel Dallstream <sadallst@microsoft.com>
Reviewed-by: Daniel Bratell <bratell@opera.com>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Tommi <tommi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666537}

third_party/blink/renderer/modules/speech/speech_synthesis_event.idl

@@ -30,7 +30,7 @@
 ] interface SpeechSynthesisEvent : Event {
     readonly attribute SpeechSynthesisUtterance utterance;
     readonly attribute unsigned long charIndex;
-    [RuntimeEnabled=SpeechSynthesisEventCharLength] readonly attribute unsigned long charLength;
+    readonly attribute unsigned long charLength;
     readonly attribute float elapsedTime;
     readonly attribute DOMString name;
 };

third_party/blink/renderer/modules/speech/speech_synthesis_event_init.idl

@@ -6,7 +6,7 @@
 dictionary SpeechSynthesisEventInit : EventInit {
     required SpeechSynthesisUtterance utterance;
     unsigned long charIndex = 0;
-    [RuntimeEnabled=SpeechSynthesisEventCharLength] unsigned long charLength = 0;
+    unsigned long charLength = 0;
     float elapsedTime = 0;
     DOMString name = "";
 };

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1429,10 +1429,6 @@
       name: "SmsReceiver",
       status: "experimental",
     },
-    {
-      name: "SpeechSynthesisEventCharLength",
-      status: "experimental",
-    },
     // Used as argument in attribute of stable-release functions/interfaces
     // where a runtime-enabled feature name is required for correct IDL syntax.
     // This is a global flag; do not change its status.

third_party/blink/web_tests/virtual/stable/webexposed/global-interface-listing-expected.txt

@@ -6607,6 +6607,7 @@ interface SpeechSynthesisErrorEvent : SpeechSynthesisEvent
 interface SpeechSynthesisEvent : Event
     attribute @@toStringTag
     getter charIndex
+    getter charLength
     getter elapsedTime
     getter name
     getter utterance