Bump lodash from 4.17.19 to 4.17.21 in /backend

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.19 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](https://github.com/lodash/lodash/compare/4.17.19...4.17.21)

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

backend/package.json

@@ -19,7 +19,7 @@
 		"jsonwebtoken": "^8.5.1",
 		"knex": "^0.20.13",
 		"liquidjs": "^9.11.10",
-		"lodash": "^4.17.19",
+		"lodash": "^4.17.21",
 		"moment": "^2.24.0",
 		"mysql": "^2.18.1",
 		"node-rsa": "^1.0.8",

backend/yarn.lock

@@ -2024,10 +2024,10 @@ lodash.once@^4.0.0:
   resolved "https://registry.yarnpkg.com/lodash.once/-/lodash.once-4.1.1.tgz#0dd3971213c7c56df880977d504c88fb471a97ac"
   integrity sha1-DdOXEhPHxW34gJd9UEyI+0cal6w=
 
-lodash@^4.17.14, lodash@^4.17.15, lodash@^4.17.19:
-  version "4.17.19"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.19.tgz#e48ddedbe30b3321783c5b4301fbd353bc1e4a4b"
-  integrity sha512-JNvd8XER9GQX0v2qJgsaN/mzFCNA5BRe/j8JN9d+tWyGLSodKQHKFicdwNYzWwI3wjRnaKPsGj1XkBjx/F96DQ==
+lodash@^4.17.14, lodash@^4.17.15, lodash@^4.17.19, lodash@^4.17.21:
+  version "4.17.21"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.21.tgz#679591c564c3bffaae8454cf0b3df370c3d6911c"
+  integrity sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg==
 
 lowercase-keys@^1.0.0, lowercase-keys@^1.0.1:
   version "1.0.1"