fix: correct scroll-timeline-axis and mask-repeat initial value (#622)

1. The current scroll-animations spec says the initial value is 'block'.
https://w3c.github.io/csswg-drafts/scroll-animations/#scroll-timeline-axis.
`none` does not look like a legal value to me.
2. The `mask-repeat` initial value is `repeat`:
https://drafts.fxtf.org/css-masking/#the-mask-repeat
You can even check that on the MDN page that says the initial value is
`no-repeat` by setting `mask-repeat` to `initial`.

css/properties.json

@@ -6624,7 +6624,7 @@
     "groups": [
       "CSS Masking"
     ],
-    "initial": "no-repeat",
+    "initial": "repeat",
     "appliesto": "allElementsSVGContainerElements",
     "computed": "consistsOfTwoDimensionKeywords",
     "order": "perGrammar",
@@ -8627,7 +8627,7 @@
     "groups": [
       "CSS Animations"
     ],
-    "initial": "none",
+    "initial": "block",
     "appliesto": "scrollContainers",
     "computed": "asSpecified",
     "order": "perGrammar",