Tests: Remove a workaround for a Firefox XML parsing issue

Firefox 96-100 used to report the column number smaller by 2 than it should
in the `parsererror` element generated for invalid XML documents. Since that
version range is unsupported now and it includes no ESR versions, the workaround
can now be dropped.

Closes gh-5109
Ref gh-5018

(cherry picked from commit e7ffe1f)

test/unit/core.js

@@ -1454,13 +1454,7 @@ QUnit[
 	column = columnMatch && columnMatch[ 1 ];
 
 	assert.strictEqual( line, "1", "reports error line" );
-
-	// Support: Firefox 96-97+
-	// Newer Firefox may report the column number smaller by 2 than it should.
-	// Accept both values until the issue is fixed.
-	// See https://bugzilla.mozilla.org/show_bug.cgi?id=1751796
-	assert.ok( [ "9", "11" ].indexOf( column ) > -1, "reports error column" );
-	// assert.strictEqual( column, "11", "reports error column" );
+	assert.strictEqual( column, "11", "reports error column" );
 } );
 
 testIframe(