test workflow: use an explicit matrix variable instead of an inline value

zizmor complains that the previous approach was considered "obfuscation".

Using a matrix value instead as suggested in #13733 (comment).

Author: nicoddemus

.github/workflows/test.yml

@@ -55,6 +55,15 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        xfail: [
+          "windows-py310-pluggy",
+          "windows-py313",
+          "ubuntu-py310-pluggy",
+          "ubuntu-py310-freeze",
+          "ubuntu-py313",
+          "macos-py310",
+          "macos-py313"
+        ]
         name: [
           "windows-py310-unittest-asynctest",
           "windows-py310-unittest-twisted24",
@@ -243,18 +252,7 @@ jobs:
     continue-on-error: >-
       ${{
         contains(
-          fromJSON(
-            '[
-              "windows-py310-pluggy",
-              "windows-py313",
-              "ubuntu-py310-pluggy",
-              "ubuntu-py310-freeze",
-              "ubuntu-py313",
-              "macos-py310",
-              "macos-py313"
-            ]'
-          ),
-          matrix.name
+          fromJSON(matrix.xfail), matrix.name
         )
         && true
         || false