Bump lodash from 4.17.11 to 4.17.15 in /tools/contributors (#47)

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.11 to 4.17.15.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.11...4.17.15)

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

Author: dependabot[bot]

tools/contributors/yarn.lock

@@ -204,9 +204,9 @@ jsprim@^1.2.2:
     verror "1.10.0"
 
 lodash@^4.13.1:
-  version "4.17.11"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.11.tgz#b39ea6229ef607ecd89e2c8df12536891cac9b8d"
-  integrity sha512-cQKh8igo5QUhZ7lg38DYWAxMvjSAKG0A8wGSVimP07SIUEK2UO+arSRKbRZWtelMtN5V0Hkwh5ryOto/SshYIg==
+  version "4.17.15"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
+  integrity sha512-8xOcRHvCjnocdS5cpwXQXVzmmh5e5+saE2QGoeQmbKmRS6J3VQppPOIt0MnmE+4xlZoumy0GPG0D0MVIQbNA1A==
 
 mime-db@~1.36.0:
   version "1.36.0"