fix(vexflow): update vexflow to 1.2.90, fixing rests displayed twice (see OSMD function test invisible notes)

visual regression tests run for the first time for this update.

only visual change for the samples was in the invisible notes function test,
where instead of double rest notes on the same beat,
it now only displays one rest, which looks better.

package.json

@@ -58,7 +58,7 @@
     "loglevel": "^1.5.0",
     "svg2pdf.js": "^1.5.0",
     "typescript-collections": "^1.3.3",
-    "vexflow": "1.2.89"
+    "vexflow": "1.2.90"
   },
   "devDependencies": {
     "@types/chai": "^4.2.9",