Upgrade find-versions to 4.0.0 (#837)

`find-versions` 4.0.0 depends on `^3.1.2` of `semver-regex`. Previous
versions of `semver-regex` contained a [vulnernability][0]. This was
unlikely to affect `husky` because of how `find-versions` is used, but
the only breaking change in `find-versions` is increasing the minimum
Node.js verison to 10, which is the same as Husky's minimum.

[0]: https://app.snyk.io/vuln/SNYK-JS-SEMVERREGEX-1047770

package.json

@@ -53,7 +53,7 @@
     "ci-info": "^2.0.0",
     "compare-versions": "^3.6.0",
     "cosmiconfig": "^7.0.0",
-    "find-versions": "^3.2.0",
+    "find-versions": "^4.0.0",
     "opencollective-postinstall": "^2.0.2",
     "pkg-dir": "^4.2.0",
     "please-upgrade-node": "^3.2.0",