remove now-unused dependencies

package.json

@@ -228,7 +228,6 @@
     "chai": "4.2.0",
     "chai-exclude": "2.0.2",
     "coffeescript": "2.5.1",
-    "core-js": "3.8.1",
     "coveralls": "3.1.0",
     "dependency-lint": "6.0.0",
     "dirty-chai": "2.0.1",
@@ -247,7 +246,6 @@
     "ndjson-parse": "1.0.4",
     "nyc": "15.1.0",
     "prettier": "2.2.1",
-    "regenerator-runtime": "0.13.7",
     "semver": "7.3.4",
     "sinon": "9.2.2",
     "sinon-chai": "3.5.0",

yarn.lock

@@ -1381,11 +1381,6 @@ cookie@0.4.0:
   resolved "https://registry.yarnpkg.com/cookie/-/cookie-0.4.0.tgz#beb437e7022b3b6d49019d088665303ebe9c14ba"
   integrity sha512-+Hp8fLp57wnUSt0tY0tHEXh4voZRDnoIrZPqlo3DPiI4y9lwg/jqx+1Om94/W6ZaPDOUbnjOt/99w66zk+l1Xg==
 
-core-js@3.8.1:
-  version "3.8.1"
-  resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.8.1.tgz#f51523668ac8a294d1285c3b9db44025fda66d47"
-  integrity sha512-9Id2xHY1W7m8hCl8NkhQn5CufmF/WuR30BTRewvCXc1aZd3kMECwNZ69ndLbekKfakw9Rf2Xyc+QR6E7Gg+obg==
-
 core-js@^2.6.5:
   version "2.6.11"
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.11.tgz#38831469f9922bded8ee21c9dc46985e0399308c"
@@ -3696,7 +3691,7 @@ readdirp@~3.5.0:
   dependencies:
     picomatch "^2.2.1"
 
-regenerator-runtime@0.13.7, regenerator-runtime@^0.13.4:
+regenerator-runtime@^0.13.4:
   version "0.13.7"
   resolved "https://registry.yarnpkg.com/regenerator-runtime/-/regenerator-runtime-0.13.7.tgz#cac2dacc8a1ea675feaabaeb8ae833898ae46f55"
   integrity sha512-a54FxoJDIr27pgf7IgeQGxmqUNYrcV338lf/6gH456HZ/PhX+5BcwHXG9ajESmwe6WRO0tAzRUrRmNONWgkrew==