Update uswds dep to fix sub-dep security vulnerability

There was a security vulnerability in `cached-path-relative`: https://hackerone.com/reports/390847

The package is a dependency of `browserify` which is a dependency of
`uswds`, which is one of our dependencies. Upgrading `uswds` to the
latest version installs the latest version of `cached-path-relative`
that has the security fix.

This update also requires bringing in a new static image that was
recently added in `uswds`.

package.json

@@ -19,7 +19,7 @@
     "ramda": "^0.25.0",
     "svg-innerhtml": "^1.1.0",
     "text-mask-addons": "^3.8.0",
-    "uswds": "^1.6.3",
+    "uswds": "^1.6.9",
     "v-tooltip": "^2.0.0-rc.33",
     "vue": "2.5.15",
     "vue-text-mask": "^6.1.2"