fix(Windows): Move rnpm-plugin-windows to devDependencies. (#1266)

package.json

   "dependencies": {
     "escape-string-regexp": "2.0.0",
     "invariant": "2.2.4",
-    "rnpm-plugin-windows": "^0.5.1-0",
     "uuid": "^7.0.3"
   },
   "devDependencies": {
     "react-native": "0.61.5",
     "react-native-macos": "0.60.0-microsoft.49",
     "react-native-windows": "^0.61.0-beta.58",
+    "rnpm-plugin-windows": "^0.5.1-0",
     "semantic-release": "15.13.24",
     "typescript": "3.6.2"
   },