Bump bson from 1.1.3 to 1.1.6 in /backend

Bumps [bson](https://github.com/mongodb/js-bson) from 1.1.3 to 1.1.6.
- [Release notes](https://github.com/mongodb/js-bson/releases)
- [Changelog](https://github.com/mongodb/js-bson/blob/v1.1.6/HISTORY.md)
- [Commits](mongodb/js-bson@v1.1.3...v1.1.6)

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

Author: dependabot[bot]

backend/yarn.lock

@@ -114,9 +114,9 @@ braces@~3.0.2:
     fill-range "^7.0.1"
 
 bson@^1.1.1, bson@~1.1.1:
-  version "1.1.3"
-  resolved "https://registry.yarnpkg.com/bson/-/bson-1.1.3.tgz#aa82cb91f9a453aaa060d6209d0675114a8154d3"
-  integrity sha512-TdiJxMVnodVS7r0BdL42y/pqC9cL2iKynVwA0Ho3qbsQYr428veL3l7BQyuqiw+Q5SqqoT0m4srSY/BlZ9AxXg==
+  version "1.1.6"
+  resolved "https://registry.yarnpkg.com/bson/-/bson-1.1.6.tgz#fb819be9a60cd677e0853aee4ca712a785d6618a"
+  integrity sha512-EvVNVeGo4tHxwi8L6bPj3y3itEvStdwvvlojVxxbyYfoaxJ6keLgrTuKdyfEAszFK+H3olzBuafE0yoh0D1gdg==
 
 bytes@3.1.0:
   version "3.1.0"