Bump @types/socket.io from 2.1.4 to 2.1.11 in /backend

Bumps [@types/socket.io](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/socket.io) from 2.1.4 to 2.1.11.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/socket.io)

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

Author: dependabot-preview[bot]

backend/package.json

@@ -14,7 +14,7 @@
   },
   "devDependencies": {
     "@types/lodash": "4.14.160",
-    "@types/socket.io": "^2.1.4",
+    "@types/socket.io": "^2.1.11",
     "@types/uuid": "^7.0.0",
     "ts-node-dev": "^1.0.0-pre.60",
     "ts-node": "^9.0.0",

backend/yarn.lock

@@ -2,6 +2,13 @@
 # yarn lockfile v1
 
 
+"@types/engine.io@*":
+  version "3.1.4"
+  resolved "https://registry.yarnpkg.com/@types/engine.io/-/engine.io-3.1.4.tgz#3d9472711d179daa7c95c051e50ad411e18a9bdc"
+  integrity sha512-98rXVukLD6/ozrQ2O80NAlWDGA4INg+tqsEReWJldqyi2fulC9V7Use/n28SWgROXKm6003ycWV4gZHoF8GA6w==
+  dependencies:
+    "@types/node" "*"
+
 "@types/[email protected]":
   version "4.14.160"
   resolved "https://registry.yarnpkg.com/@types/lodash/-/lodash-4.14.160.tgz#2f1bba6500bc3cb9a732c6d66a083378fb0b0b29"
@@ -12,11 +19,12 @@
   resolved "https://registry.yarnpkg.com/@types/node/-/node-13.9.0.tgz#5b6ee7a77faacddd7de719017d0bc12f52f81589"
   integrity sha512-0ARSQootUG1RljH2HncpsY2TJBfGQIKOOi7kxzUY6z54ePu/ZD+wJA8zI2Q6v8rol2qpG/rvqsReco8zNMPvhQ==
 
-"@types/socket.io@^2.1.4":
-  version "2.1.4"
-  resolved "https://registry.yarnpkg.com/@types/socket.io/-/socket.io-2.1.4.tgz#674e7bc193c5ccdadd4433f79f3660d31759e9ac"
-  integrity sha512-cI98INy7tYnweTsUlp8ocveVdAxENUThO0JsLSCs51cjOP2yV5Mqo5QszMDPckyRRA+PO6+wBgKvGvHUCc23TQ==
+"@types/socket.io@^2.1.11":
+  version "2.1.11"
+  resolved "https://registry.yarnpkg.com/@types/socket.io/-/socket.io-2.1.11.tgz#e0d6759880e5f9818d5297a3328b36641bae996b"
+  integrity sha512-bVprmqPhJMLb9ZCm8g0Xy8kwBFRbnanOWSxzWkDkkIwxTvud5tKMfAJymXX6LQbizUKCS1yima7JM4BeLqjNqA==
   dependencies:
+    "@types/engine.io" "*"
     "@types/node" "*"
 
 "@types/strip-bom@^3.0.0":