fix: descriptions of discrete animation behavior between visible and hidden (#690)

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### Description

In #688, part of the work was to add
descriptions of the new specific animation behavior of certain
"discrete" animated properties — `display`, `content-visibility`, and
`overlay` — when animating from a hidden state or a visible state.
However, on talking to some Chrome engineering folks about this, I
realized that some of my descriptions were not quite right.

This PR aims to fix those descriptions.

The description I was sent by the Chrome engineering folk is as follows:

"The idea behind "p = 1" is that during transitions between certain
values for certain properties which we consider invisible to visible or
vice versa, the browser will automatically choose the "visible" option
for the duration of the animation it creates.
For example, if you transition from "display:none" to "display:block",
the element will be "display:block" for the entire animation created by
the transition.
And likewise if you transition from "display:block" to "display:none",
the element will be "display:block" for the entire animation created by
the transition.
However, if you transition from "display:flex" to "display:block", the
element's display value will switch halfway through the animation.
This behavior is applied to content-visibility:hidden, display:none,
visibility:hidden, and overlay:none."

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### Motivation

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Author: chrisdavidmills

css/properties.json

@@ -4483,7 +4483,7 @@
     "syntax": "visible | auto | hidden",
     "media": "all",
     "inherited": false,
-    "animationType": "discreteHiddenSwapAt0",
+    "animationType": "discreteButVisibleForDurationWhenAnimatedHidden",
     "percentages": "no",
     "groups": [
       "CSS Containment"
@@ -4582,7 +4582,7 @@
     "syntax": "[ <display-outside> || <display-inside> ] | <display-listitem> | <display-internal> | <display-box> | <display-legacy>",
     "media": "all",
     "inherited": false,
-    "animationType": "discreteNoneSwapAt0",
+    "animationType": "discreteButVisibleForDurationWhenAnimatedNone",
     "percentages": "no",
     "groups": [
       "CSS Display"
@@ -7619,7 +7619,7 @@
     "syntax": "none | auto",
     "media": "visual",
     "inherited": false,
-    "animationType": "discreteSwapAt1",
+    "animationType": "discreteButVisibleForDurationWhenAnimatedNone",
     "percentages": "no",
     "groups": [
       "CSS Positioning"

css/properties.schema.json

@@ -21,9 +21,8 @@
         "byComputedValueTypeNormalAnimatesAsObliqueZeroDeg",
         "color",
         "discrete",
-        "discreteHiddenSwapAt0",
-        "discreteNoneSwapAt0",
-        "discreteSwapAt1",
+        "discreteButVisibleForDurationWhenAnimatedHidden",
+        "discreteButVisibleForDurationWhenAnimatedNone",
         "eachOfShorthandPropertiesExceptUnicodeBiDiAndDirection",
         "filterList",
         "fontStretch",

l10n/css.json

@@ -654,14 +654,11 @@
     "fr": "discrète",
     "ja": "離散値"
   },
-  "discreteHiddenSwapAt0": {
-    "en-US": "Discrete behavior but when animating from <code>hidden</code> swaps to end value at progress > 0 rather than 0.5"
+  "discreteButVisibleForDurationWhenAnimatedHidden": {
+    "en-US": "Discrete behavior except when animating to or from <code>hidden</code> is visible for the entire duration"
   },
-  "discreteNoneSwapAt0": {
-    "en-US": "Discrete behavior but when animating from <code>none</code> swaps to end value at progress > 0 rather than 0.5"
-  },
-  "discreteSwapAt1": {
-    "en-US": "Discrete behavior but swaps to end value at progress 1 rather than 0.5"
+  "discreteButVisibleForDurationWhenAnimatedNone": {
+    "en-US": "Discrete behavior except when animating to or from <code>none</code> is visible for the entire duration"
   },
   "eachOfShorthandPropertiesExceptUnicodeBiDiAndDirection": {
     "de": "wie jede der Kurzschreibweisen Eigenschaften (alle Eigenschaften außer {{cssxref(\"unicode-bidi\")}} und {{cssxref(\"direction\")}})",