Bump snyk from 1.252.0 to 1.256.0

Bumps [snyk](https://github.com/snyk/snyk) from 1.252.0 to 1.256.0.
- [Release notes](https://github.com/snyk/snyk/releases)
- [Changelog](https://github.com/snyk/snyk/blob/master/.releaserc)
- [Commits](https://github.com/snyk/snyk/compare/v1.252.0...v1.256.0)

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

package.json

@@ -13,7 +13,7 @@
     "jstree": "^3.3.8",
     "opensans-webkit": "^1.0.1",
     "popper.js": "^1.15.0",
-    "snyk": "^1.189.0",
+    "snyk": "^1.256.0",
     "underscore": "^1.9.1",
     "vis": "^4.21.0",
     "webpack-merge": "^4.1.4"