Auto merge of #17839 - heycam:opacity-smil, r=hiro

style: allow out-of-range opacity values for SMIL animations

From https://bugzilla.mozilla.org/show_bug.cgi?id=1371150.

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components/style/properties/properties.mako.rs

@@ -2996,6 +2996,7 @@ where
         cached_system_font: None,
         in_media_query: false,
         quirks_mode: quirks_mode,
+        for_smil_animation: false,
     };
 
     let ignore_colors = !device.use_document_colors();