Fix wiggle arpeggio down vtest + collect_artifacts

by not using `SymId::wiggleArpeggiatoDownArrow` in a `symbolLine()`
for an `ArpeggioType::DOWN`, but using the same line as
for `ArpeggioType::UP`, just turned upside down.

Author: Jojo-Schmitz

libmscore/arpeggio.cpp

@@ -173,8 +173,8 @@ void Arpeggio::layout()
     break;
 
     case ArpeggioType::DOWN: {
-        symbolLine(SymId::wiggleArpeggiatoDownArrow, SymId::wiggleArpeggiatoDown);
-        // string is rotated +90 degrees
+        symbolLine(SymId::wiggleArpeggiatoUpArrow, SymId::wiggleArpeggiatoUp);
+        // string is rotated +90 degrees (so that UpArrow turns into a DownArrow)
         QRectF r(symBbox(symbols));
         setbbox(QRectF(0.0, r.x() + y1, r.height(), r.width()));
     }