Bump http-cache-semantics and lerna

Bumps [http-cache-semantics](https://github.com/kornelski/http-cache-semantics) to 4.1.1 and updates ancestor dependency [lerna](https://github.com/lerna/lerna/tree/HEAD/core/lerna). These dependencies need to be updated together.


Updates `http-cache-semantics` from 3.8.1 to 4.1.1
- [Release notes](https://github.com/kornelski/http-cache-semantics/releases)
- [Commits](https://github.com/kornelski/http-cache-semantics/commits)

Updates `lerna` from 3.20.2 to 6.4.1
- [Release notes](https://github.com/lerna/lerna/releases)
- [Changelog](https://github.com/lerna/lerna/blob/v6.4.1/core/lerna/CHANGELOG.md)
- [Commits](https://github.com/lerna/lerna/commits/v6.4.1/core/lerna)

---
updated-dependencies:
- dependency-name: http-cache-semantics
  dependency-type: indirect
- dependency-name: lerna
  dependency-type: direct:development
...

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

package.json

@@ -100,7 +100,7 @@
     "jest-json-schema": "^2.0.1",
     "jest-watch-typeahead": "^0.2.0",
     "jsdoc": "^3.6.3",
-    "lerna": "^3.20.2",
+    "lerna": "^6.4.1",
     "mkdirp": "^0.5.1",
     "prettier": "^1.18.2",
     "prettier-plugin-solidity": "^1.0.0-alpha.22",