Remove unused dev package

Author: michaeldzjap

package-lock.json

@@ -57,7 +57,6 @@
     "react-dom": "^16.13.1",
     "rollup": "^2.26.10",
     "rollup-plugin-eslint": "^7.0.0",
-    "rollup-plugin-sourcemaps": "^0.6.2",
     "rollup-plugin-terser": "^7.0.2",
     "rollup-plugin-uglify": "^6.0.4"
   },