Bump validator from 13.15.15 to 13.15.20 in /backend/typescript

Bumps [validator](https://github.com/validatorjs/validator.js) from 13.15.15 to 13.15.20.
- [Release notes](https://github.com/validatorjs/validator.js/releases)
- [Changelog](https://github.com/validatorjs/validator.js/blob/master/CHANGELOG.md)
- [Commits](validatorjs/validator.js@13.15.15...13.15.20)

---
updated-dependencies:
- dependency-name: validator
  dependency-version: 13.15.20
  dependency-type: indirect
...

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

Author: dependabot[bot]

backend/typescript/yarn.lock

@@ -8094,9 +8094,9 @@ v8-to-istanbul@^8.1.0:
     source-map "^0.7.3"
 
 validator@^13.9.0:
-  version "13.15.15"
-  resolved "https://registry.npmjs.org/validator/-/validator-13.15.15.tgz"
-  integrity sha512-BgWVbCI72aIQy937xbawcs+hrVaN/CZ2UwutgaJ36hGqRrLNM+f5LUT/YPRbo8IV/ASeFzXszezV+y2+rq3l8A==
+  version "13.15.20"
+  resolved "https://registry.yarnpkg.com/validator/-/validator-13.15.20.tgz#054e9238109538a1bf46ae3e1290845a64fa2186"
+  integrity sha512-KxPOq3V2LmfQPP4eqf3Mq/zrT0Dqp2Vmx2Bn285LwVahLc+CsxOM0crBHczm8ijlcjZ0Q5Xd6LW3z3odTPnlrw==
 
 value-or-promise@1.0.11:
   version "1.0.11"