Bump @types/bn.js from 4.11.6 to 5.1.0

Bumps [@types/bn.js](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/bn.js) from 4.11.6 to 5.1.0.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/bn.js)

---
updated-dependencies:
- dependency-name: "@types/bn.js"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package-lock.json

@@ -14,7 +14,7 @@
   "license": "ISC",
   "dependencies": {
     "@polkadot/api": "^6.3.2-11",
-    "@types/bn.js": "^4.11.6",
+    "@types/bn.js": "^5.1.0",
     "bignumber.js": "^9.0.1",
     "commander": "^7.2.0",
     "cron": "^1.8.2",