chore(deps): bump validator from 13.7.0 to 13.15.23 in /backend

Bumps [validator](https://github.com/validatorjs/validator.js) from 13.7.0 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@13.7.0...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

@@ -6830,9 +6830,9 @@ validate-npm-package-license@^3.0.1:
     spdx-expression-parse "^3.0.0"
 
 validator@^13.1.1:
-  version "13.7.0"
-  resolved "https://registry.yarnpkg.com/validator/-/validator-13.7.0.tgz#4f9658ba13ba8f3d82ee881d3516489ea85c0857"
-  integrity sha512-nYXQLCBkpJ8X6ltALua9dRrZDHVYxjJ1wgskNt1lH9fzGjs3tgojGSCBjmEPwkWS1y29+DrizMTW19Pr9uB2nw==
+  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"