fix: packages/letter/package.json & packages/letter/.snyk to reduce v…

…ulnerabilities

The following vulnerabilities are fixed with a Snyk patch:
- https://snyk.io/vuln/SNYK-JS-LODASH-567746

packages/letter/package.json

@@ -37,7 +37,8 @@
     "redux": "^4.0.5",
     "redux-actions": "^2.6.5",
     "redux-immutable": "^4.0.0",
-    "reselect": "^4.0.0"
+    "reselect": "^4.0.0",
+    "snyk": "^1.317.0"
   },
   "devDependencies": {
     "chai": "^4.2.0",
@@ -57,7 +58,6 @@
     "redux-mock-store": "^1.5.4",
     "redux-thunk": "^2.3.0",
     "sinon": "^9.0.2",
-    "snyk": "^1.316.2",
     "webpack": "^4.43.0"
   },
   "directories": {