Bug 1659916 [wpt PR 25101] - Update interfaces/css-typed-om.idl, a=testonly

Automatic update from web-platform-tests
Update interfaces/css-typed-om.idl (#25101)

Source: https://github.com/tidoust/reffy-reports/blob/4cba804/ed/idl/css-typed-om.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/719138445
--

wpt-commits: cfe894e7254fa0666b553a450dec3d336f052f01
wpt-pr: 25101

testing/web-platform/tests/interfaces/css-typed-om.idl

@@ -23,10 +23,10 @@ interface StylePropertyMapReadOnly {
 
 [Exposed=Window]
 interface StylePropertyMap : StylePropertyMapReadOnly {
-    void set(USVString property, (CSSStyleValue or USVString)... values);
-    void append(USVString property, (CSSStyleValue or USVString)... values);
-    void delete(USVString property);
-    void clear();
+    undefined set(USVString property, (CSSStyleValue or USVString)... values);
+    undefined append(USVString property, (CSSStyleValue or USVString)... values);
+    undefined delete(USVString property);
+    undefined clear();
 };
 
 partial interface Element {