Change CSPViolationReportBody to dictionary (#737)

Following the changes in w3c/reporting#284 all report bodies
now need to be dictionaries, following the conclusion of
w3c/reporting#216

Author: TimvdLippe

index.bs

@@ -1632,20 +1632,18 @@ this algorithm returns normally if compilation is allowed, and throws a
   <code>ReportingObserver</code>s</a>.
 
   <pre class="idl">
-    [Exposed=Window]
-    interface CSPViolationReportBody : ReportBody {
-      [Default] object toJSON();
-      readonly attribute USVString documentURL;
-      readonly attribute USVString? referrer;
-      readonly attribute USVString? blockedURL;
-      readonly attribute DOMString effectiveDirective;
-      readonly attribute DOMString originalPolicy;
-      readonly attribute USVString? sourceFile;
-      readonly attribute DOMString? sample;
-      readonly attribute SecurityPolicyViolationEventDisposition disposition;
-      readonly attribute unsigned short statusCode;
-      readonly attribute unsigned long? lineNumber;
-      readonly attribute unsigned long? columnNumber;
+    dictionary CSPViolationReportBody : ReportBody {
+      USVString documentURL;
+      USVString? referrer;
+      USVString? blockedURL;
+      DOMString effectiveDirective;
+      DOMString originalPolicy;
+      USVString? sourceFile;
+      DOMString? sample;
+      SecurityPolicyViolationEventDisposition disposition;
+      unsigned short statusCode;
+      unsigned long? lineNumber;
+      unsigned long? columnNumber;
     };
   </pre>