Bump bn.js from 4.12.0 to 4.12.3 in /tts

Bumps [bn.js](https://github.com/indutny/bn.js) from 4.12.0 to 4.12.3.
- [Release notes](https://github.com/indutny/bn.js/releases)
- [Changelog](https://github.com/indutny/bn.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/indutny/bn.js/compare/v4.12.0...v4.12.3)

---
updated-dependencies:
- dependency-name: bn.js
  dependency-version: 4.12.3
  dependency-type: indirect
...

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

tts/package-lock.json

@@ -849,9 +849,10 @@
       "dev": true
     },
     "node_modules/bn.js": {
-      "version": "4.12.0",
-      "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-4.12.0.tgz",
-      "integrity": "sha512-c98Bf3tPniI+scsdk237ku1Dc3ujXQTSgyiPUDEOe7tRkhrqridvh8klBv0HCEso1OLOYcHuCv/cS6DNxKH+ZA=="
+      "version": "4.12.3",
+      "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-4.12.3.tgz",
+      "integrity": "sha512-fGTi3gxV/23FTYdAoUtLYp6qySe2KE3teyZitipKNRuVYcBkoP/bB3guXN/XVKUe9mxCHXnc9C4ocyz8OmgN0g==",
+      "license": "MIT"
     },
     "node_modules/brace-expansion": {
       "version": "1.1.11",