Revert "require @babel/traverse before 7.21.4 to work around its bug"

Instead, require <7.21.4 or ≥7.21.5 since they say they
fixed it: babel/babel#15579

This reverts commit 05a0b8a.
This reverts commit 3a3f81f.

package.json

@@ -33,10 +33,9 @@
   "homepage": "https://github.com/danvk/dygraphs",
   "devDependencies": {
     "@babel/cli": "^7.19.3",
-    "@babel/core": "^7.20.2 <7.21.4",
+    "@babel/core": ">=7.20.2 <7.21.4 || ^7.21.5",
     "@babel/plugin-transform-strict-mode": "^7.18.6",
     "@babel/preset-env": "^7.20.2",
-    "@babel/traverse": "<7.21.4",
     "babel-plugin-add-module-exports": "^1.0.4",
     "browser-pack": "^6.1.0",
     "browserify": "^17.0.0",