Bump shell-quote from 1.6.1 to 1.7.3

Bumps [shell-quote](https://github.com/substack/node-shell-quote) from 1.6.1 to 1.7.3.
- [Release notes](https://github.com/substack/node-shell-quote/releases)
- [Changelog](https://github.com/substack/node-shell-quote/blob/master/CHANGELOG.md)
- [Commits](https://github.com/substack/node-shell-quote/compare/1.6.1...1.7.3)

---
updated-dependencies:
- dependency-name: shell-quote
  dependency-type: direct:production
...

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

Author: dependabot[bot]

package-lock.json

@@ -39,7 +39,7 @@
     "redis": "3.1.x",
     "request": "2.x",
     "requestretry": "1.x",
-    "shell-quote": "1.6.1",
+    "shell-quote": "1.7.3",
     "shortid": "^2.2.15",
     "twitter": "^1.7.1",
     "underscore": "1.x",