Bump @babel/preset-env from 7.6.2 to 7.6.3 in /slides

Bumps [@babel/preset-env](https://github.com/babel/babel) from 7.6.2 to 7.6.3.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](babel/babel@v7.6.2...v7.6.3)

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Author: dependabot-preview[bot]

slides/package-lock.json

@@ -8,7 +8,7 @@
   },
   "devDependencies": {
     "@babel/core": "^7.6.2",
-    "@babel/preset-env": "^7.6.2",
+    "@babel/preset-env": "^7.6.3",
     "babel-loader": "^8.0.6",
     "css-loader": "^3.2.0",
     "file-loader": "^4.2.0",