Bump node-fetch from 2.6.6 to 2.6.7 in /examples/hardhat

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) from 2.6.6 to 2.6.7.
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](node-fetch/node-fetch@v2.6.6...v2.6.7)

---
updated-dependencies:
- dependency-name: node-fetch
  dependency-type: indirect
...

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

Author: dependabot[bot]

examples/hardhat/yarn.lock

@@ -2086,9 +2086,9 @@ [email protected]:
     semver "^5.7.0"
 
 node-fetch@^2.6.0:
-  version "2.6.6"
-  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.6.tgz#1751a7c01834e8e1697758732e9efb6eeadfaf89"
-  integrity sha512-Z8/6vRlTUChSdIgMa51jxQ4lrw/Jy5SOW10ObaA47/RElsAN2c5Pn8bTgFGWn/ibwzXTE8qwr1Yzx28vsecXEA==
+  version "2.6.7"
+  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.7.tgz#24de9fba827e3b4ae44dc8b20256a379160052ad"
+  integrity sha512-ZjMPFEfVx5j+y2yF35Kzx5sF7kDzxuDj6ziH4FFbOp87zKDZNx8yExJIb05OGF4Nlt9IHFIMBkRl41VdvcNdbQ==
   dependencies:
     whatwg-url "^5.0.0"