Bump handlebars from 4.7.3 to 4.7.6 in /build

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.7.3 to 4.7.6.
- [Release notes](https://github.com/wycats/handlebars.js/releases)
- [Changelog](https://github.com/wycats/handlebars.js/blob/master/release-notes.md)
- [Commits](handlebars-lang/handlebars.js@v4.7.3...v4.7.6)

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

build/package.json

@@ -11,7 +11,7 @@
   "contributors": [],
   "dependencies": {},
   "devDependencies": {
-    "handlebars": "^4.7.3",
+    "handlebars": "^4.7.6",
     "jasmine-core": "~2.5.2",
     "jasmine-sinon": "^0.4.0",
     "jsdoc": "^3.6.3",