Bump acorn from 7.1.0 to 7.1.1 in /backend

Bumps [acorn](https://github.com/acornjs/acorn) from 7.1.0 to 7.1.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@7.1.0...7.1.1)

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

Author: dependabot[bot]

backend/yarn.lock

@@ -37,9 +37,9 @@ acorn-jsx@^5.1.0:
   integrity sha512-tMUqwBWfLFbJbizRmEcWSLw6HnFzfdJs2sOJEOwwtVPMoH/0Ay+E703oZz78VSXZiiDcZrQ5XKjPIUQixhmgVw==
 
 acorn@^7.1.0:
-  version "7.1.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.0.tgz#949d36f2c292535da602283586c2477c57eb2d6c"
-  integrity sha512-kL5CuoXA/dgxlBbVrflsflzQ3PAas7RYZB52NOm/6839iVYJgKMJ3cQJD+t2i5+qFa8h3MDpEOJiS64E8JLnSQ==
+  version "7.1.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.1.tgz#e35668de0b402f359de515c5482a1ab9f89a69bf"
+  integrity sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==
 
 ajv@^6.10.0, ajv@^6.10.2, ajv@^6.11.0:
   version "6.11.0"