downgrade regenerator-runtime due to unsafe eval usages (#1062)

This commit downgrades regenerator-runtime from
^0.13.3 (currently 0.13.7) to being pinned to exactly
0.13.1. This is because there is a change in 0.13.2 which
adds back in a Function() constructor to define
regenerator runtime globally.
See #369 https://github.com/facebook/regenerator/commits/master/packages/regenerator-runtime

T=https://yextops.zendesk.com/agent/tickets/347915
TEST=manual

tested with a local apache httpd server on a searchbar only page
added below line to .htaccess, which sets the CSP to
the same as Syncreon

also test csp with a `<meta>` tag

tested both answers.js, answers.min.js, answers-modern.js, and answers-modern.min.js

double checked that our code still runs correctly in ie11, for both a searchbar only
page with no unsafe-eval csp, and a regular page with facets and results
that allows unsafe eval

package.json

@@ -12,7 +12,7 @@
     "kind-of": "^6.0.3",
     "lodash.clonedeep": "^4.5.0",
     "markdown-it-for-inline": "^0.1.1",
-    "regenerator-runtime": "^0.13.3",
+    "regenerator-runtime": "0.13.1",
     "template-helpers": "^1.0.1"
   },
   "devDependencies": {