Tests: the Devanagari fallback-glyph test passes when the fallback face substitutes the vowel sign

`the_fallback_glyph_of_a_consonant_after_its_vowel_sign_is_reported` expected
the fallback face's cmap glyph for the vowel sign I. On the Ubuntu runner the
fallback face is Noto Sans Devanagari, whose shaping draws the sign with
another glyph (545 instead of 32), so the test failed on `main`. It now checks
that two glyphs are drawn in Ka's cluster, the first is not Ka's and the
second is, and keeps the `text.glyphAlternates` checks.

Fixes #5750

crates/engine/src/tests/textedit.rs

@@ -2823,9 +2823,11 @@ fn the_fallback_glyph_of_a_consonant_after_its_vowel_sign_is_reported() {
     let glyphs = vectorcraft_text::layout(db, &obj(&s, open)).glyphs;
     let fallback = db.face_by_id(glyphs[0].font_id).expect("the fallback face");
     assert_ne!(fallback.id(), requested.id());
-    let (ka, sign) = (fallback.glyph_for('क'), fallback.glyph_for('\u{93F}'));
+    let ka = fallback.glyph_for('क');
     let drawn: Vec<_> = glyphs.iter().map(|g| (g.gid, g.byte)).collect();
-    assert_eq!(drawn, [(sign, 0), (ka, 0)], "the vowel sign is drawn first, in Ka's cluster ({} or {MATRA_FAMILY})", fallback.family);
+    // A face may draw the vowel sign with a glyph other than its own, so only its place is checked.
+    let sign_first = matches!(drawn[..], [(sign, 0), (k, 0)] if sign != 0 && sign != ka && k == ka);
+    assert!(sign_first, "the vowel sign is drawn first, in Ka's cluster ({} or {MATRA_FAMILY}): {drawn:?}", fallback.family);
     let query = s.execute("text.glyphAlternates", &json!({"id": open.0, "start": 0})).unwrap();
     assert_eq!(query["chosen"], json!(ka), "the fallback face's glyph for Ka");