style: Will-change should only create stacking contexts / containing blocks / etc if the property it'd change would apply

As per https://drafts.csswg.org/css-will-change/#will-change.

> If any non-initial value of a property would cause the element to
> generate a containing block for absolutely positioned elements,
> specifying that property in will-change must cause the element to
> generate a containing block for absolutely positioned elements.

But in this case the transform property wouldn't apply to the element so
there's no reason to create a stacking-context.

Differential Revision: https://phabricator.services.mozilla.com/D114121

components/style/properties/longhands/effects.mako.rs

@@ -13,7 +13,7 @@ ${helpers.predefined_type(
     "1.0",
     engines="gecko servo-2013 servo-2020",
     animation_value_type="ComputedValue",
-    flags="CREATES_STACKING_CONTEXT CAN_ANIMATE_ON_COMPOSITOR",
+    flags="CAN_ANIMATE_ON_COMPOSITOR",
     spec="https://drafts.csswg.org/css-color/#transparency",
     servo_restyle_damage = "reflow_out_of_flow",
 )}
@@ -56,7 +56,6 @@ ${helpers.predefined_type(
     animation_value_type="AnimatedFilterList",
     vector_animation_type="with_zero",
     extra_prefixes="webkit",
-    flags="CREATES_STACKING_CONTEXT FIXPOS_CB",
     spec="https://drafts.fxtf.org/filters/#propdef-filter",
 )}
 
@@ -71,7 +70,6 @@ ${helpers.predefined_type(
     separator="Space",
     animation_value_type="AnimatedFilterList",
     vector_animation_type="with_zero",
-    flags="CREATES_STACKING_CONTEXT FIXPOS_CB",
     gecko_pref="layout.css.backdrop-filter.enabled",
     spec="https://drafts.fxtf.org/filter-effects-2/#propdef-backdrop-filter",
 )}
@@ -84,6 +82,5 @@ ${helpers.single_keyword(
     engines="gecko servo-2013 servo-2020",
     gecko_enum_prefix="StyleBlend",
     animation_value_type="discrete",
-    flags="CREATES_STACKING_CONTEXT",
     spec="https://drafts.fxtf.org/compositing/#propdef-mix-blend-mode",
 )}