[webpack_v4.x.x] Fix type error

[HsuTing]

• Links to documentation: https://webpack.js.org/
• Link to GitHub or NPM: https://www.npmjs.com/package/webpack
• Type of contribution: Fix

Other notes:

Error --------------------------------------------------------------------------------------- src/utils/buildJs.js:42:26
 

Cannot call `stats.toString` with object literal bound to `options` because object type [1] is incompatible with
 boolean [2] in property `colors`.

    src/utils/buildJs.js:42:26
    42|       log(stats.toString({ logStats, colors: true }));
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 References:
    ../../flow-typed/npm/webpack_v4.x.x.js:399:9
                 v
   399|       | {
   400|       bold?: string,
   401|       cyan?: string,
   402|       green?: string,
   403|       magenta?: string,
   404|       red?: string,
   405|       yellow?: string,
   406|       ...
   407|     },
            ^ [1]
   ../../flow-typed/npm/webpack_v4.x.x.js:20:50
    20|     toString(options?: StatsOptions & { colors?: boolean, ... }): string;
                                                         ^^^^^^^ [2]

[AndrewSouthpaw]

Thanks!