Bump backbone from 1.6.0 to 1.6.1

Bumps [backbone](https://github.com/jashkenas/backbone) from 1.6.0 to 1.6.1.
- [Commits](jashkenas/backbone@1.6.0...1.6.1)

---
updated-dependencies:
- dependency-name: backbone
  dependency-version: 1.6.1
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -54,7 +54,7 @@
     "ajv": "6.12.5",
     "assert": "2.0.0",
     "async": "^3.2.6",
-    "backbone": "1.6.0",
+    "backbone": "1.6.1",
     "browserify": "^16.5.2",
     "buffer": "6.0.3",
     "chai": "4.4.1",