fix(package.json): Correction of the misspelled elm-test version

Author: halfzebra

package.json

@@ -35,7 +35,7 @@
     "dotenv": "^5.0.0",
     "elm": "0.19.0-bugfix2",
     "elm-hot-webpack-loader": "^1.0.0",
-    "elm-test": "^0.19.0-beta13",
+    "elm-test": "^0.19.0-beta8",
     "elm-webpack-loader": "^5.0.0",
     "file-loader": "^1.1.6",
     "fs-extra": "^6.0.1",