Bug 1838546 [wpt PR 40558] - Update wpt metadata, a=testonly

wpt-pr: 40558
wpt-type: metadata

testing/web-platform/meta/editing/edit-context/edit-context-property.tentative.html.ini

@@ -0,0 +1,12 @@
+[edit-context-property.tentative.html]
+  [Check the existence of HTMLElement.editContext]
+    expected: FAIL
+
+  [HTMLElement.editContext must throw a TypeError if set to something other than an EditContext]
+    expected: FAIL
+
+  [HTMLElement.editContext can be set on the shadow root elements plus canvas.]
+    expected: FAIL
+
+  [Setting HTMLElement.editContext must throw a NotSupportedError for disallowed elements]
+    expected: FAIL