Remove ESLint impliedStrict setting

With the module source type strict mode is assumed.
diff --git a/.eslintrc.js b/.eslintrc.js
index ab17f62..cb6c43c 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -10,9 +10,6 @@
   },
   parser: 'babel-eslint',
   parserOptions: {
-    ecmaFeatures: {
-      impliedStrict: true,
-    },
     ecmaVersion: 2019,
     sourceType: 'module',
   },