Update dependencies

package.json

@@ -16,7 +16,7 @@
     "test": "jest --coverage"
   },
   "devDependencies": {
-    "@polkadot/dev": "^0.20.6",
+    "@polkadot/dev": "^0.20.7",
     "@polkadot/ts": "^0.1.3"
   }
 }

yarn.lock

@@ -691,9 +691,9 @@
     lodash "^4.17.5"
     to-fast-properties "^2.0.0"
 
-"@polkadot/dev@^0.20.6":
-  version "0.20.6"
-  resolved "https://registry.yarnpkg.com/@polkadot/dev/-/dev-0.20.6.tgz#be0938f6ae1c3637696a9a41a8f2504b703f290c"
+"@polkadot/dev@^0.20.7":
+  version "0.20.7"
+  resolved "https://registry.yarnpkg.com/@polkadot/dev/-/dev-0.20.7.tgz#d62daacb0bc66bd5eee464ecc7524cf33ff2c929"
   dependencies:
     "@babel/cli" "^7.0.0-beta.51"
     "@babel/core" "^7.0.0-beta.51"