Bump validator from 13.15.20 to 13.15.23 in /backend

Bumps [validator](https://github.com/validatorjs/validator.js) from 13.15.20 to 13.15.23.
- [Release notes](https://github.com/validatorjs/validator.js/releases)
- [Changelog](https://github.com/validatorjs/validator.js/blob/master/CHANGELOG.md)
- [Commits](validatorjs/validator.js@13.15.20...13.15.23)

---
updated-dependencies:
- dependency-name: validator
  dependency-version: 13.15.23
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/yarn.lock

@@ -7911,9 +7911,9 @@ v8-to-istanbul@^9.0.1:
     convert-source-map "^2.0.0"
 
 validator@^13.7.0:
-  version "13.15.20"
-  resolved "https://registry.yarnpkg.com/validator/-/validator-13.15.20.tgz#054e9238109538a1bf46ae3e1290845a64fa2186"
-  integrity sha512-KxPOq3V2LmfQPP4eqf3Mq/zrT0Dqp2Vmx2Bn285LwVahLc+CsxOM0crBHczm8ijlcjZ0Q5Xd6LW3z3odTPnlrw==
+  version "13.15.23"
+  resolved "https://registry.yarnpkg.com/validator/-/validator-13.15.23.tgz#59a874f84e4594588e3409ab1edbe64e96d0c62d"
+  integrity sha512-4yoz1kEWqUjzi5zsPbAS/903QXSYp0UOtHsPpp7p9rHAw/W+dkInskAE386Fat3oKRROwO98d9ZB0G4cObgUyw==
 
 vary@^1, vary@~1.1.2:
   version "1.1.2"