build(deps): Bump @babel/generator from 7.6.4 to 7.7.0 (#1820)

Bumps [@babel/generator](https://github.com/babel/babel) from 7.6.4 to 7.7.0.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](babel/babel@v7.6.4...v7.7.0)

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

packages/javascript-mutator/package.json

@@ -37,7 +37,7 @@
   "homepage": "https://github.com/stryker-mutator/stryker/tree/master/packages/javascript-mutator#readme",
   "license": "Apache-2.0",
   "dependencies": {
-    "@babel/generator": "~7.6.0",
+    "@babel/generator": "~7.7.0",
     "@babel/parser": "~7.6.2",
     "@babel/traverse": "~7.6.2",
     "@stryker-mutator/api": "^2.1.0",