chore(deps-dev): bump ejs from 2.6.1 to 2.7.3 in /core

Bumps [ejs](https://github.com/mde/ejs) from 2.6.1 to 2.7.3.
- [Release notes](https://github.com/mde/ejs/releases)
- [Changelog](https://github.com/mde/ejs/blob/master/CHANGELOG.md)
- [Commits](mde/ejs@v2.6.1...v2.7.3)

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

core/package.json

@@ -53,7 +53,7 @@
     "devDependencies": {
         "@toolisticon/istanbul-coveralls": "1.0.0",
         "coveralls": "3.0.6",
-        "ejs": "2.6.1",
+        "ejs": "2.7.3",
         "eslint": "^6.1.0",
         "handlebars": "^4.4.5",
         "istanbul": "0.4.5",