fix(deps): downgrade to electron@19 to resolve macos code signing and startup crash (gitify-app#910)

Author: setchy

package.json

@@ -130,7 +130,7 @@
     "@types/react-transition-group": "4.4.10",
     "autoprefixer": "10.4.18",
     "css-loader": "6.10.0",
-    "electron": "29.1.4",
+    "electron": "19.1.9",
     "electron-builder": "24.13.3",
     "husky": "9.0.11",
     "jest": "29.7.0",