fix: package.json & yarn.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NODEFETCH-674311

package.json

@@ -71,6 +71,6 @@
     }
   },
   "dependencies": {
-    "node-fetch": "^2.1.2"
+    "node-fetch": "^2.6.1"
   }
 }

yarn.lock

@@ -972,10 +972,6 @@ babel-types@^6.18.0, babel-types@^6.19.0, babel-types@^6.24.1, babel-types@^6.26
     lodash "^4.17.4"
     to-fast-properties "^1.0.3"
 
-babel@^6.23.0:
-  version "6.23.0"
-  resolved "https://registry.yarnpkg.com/babel/-/babel-6.23.0.tgz#d0d1e7d803e974765beea3232d4e153c0efb90f4"
-
 babylon@^6.17.3, babylon@^6.18.0:
   version "6.18.0"
   resolved "https://registry.yarnpkg.com/babylon/-/babylon-6.18.0.tgz#af2f3b88fa6f5c1e4c634d1a0f8eac4f55b395e3"
@@ -4160,9 +4156,10 @@ node-dir@0.1.8:
   version "0.1.8"
   resolved "https://registry.yarnpkg.com/node-dir/-/node-dir-0.1.8.tgz#55fb8deb699070707fb67f91a460f0448294c77d"
 
-node-fetch@^2.1.2:
-  version "2.1.2"
-  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.1.2.tgz#ab884e8e7e57e38a944753cec706f788d1768bb5"
+node-fetch@^2.6.1:
+  version "2.6.1"
+  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.1.tgz#045bd323631f76ed2e2b55573394416b639a0052"
+  integrity sha512-V4aYg89jEoVRxRb2fJdAg8FHvI7cEyYdVAh94HH0UIK8oJxUfkjlDQN9RbMx+bEjP7+ggMiFRprSti032Oipxw==
 
 node-int64@^0.4.0:
   version "0.4.0"