feat!: use Terser's default for comments (#972)

Summary:
By default, Terser keeps JSDoc-style comments that contain `license` or `preserve`: https://terser.org/docs/api-reference#format-options

Note that this is potentially a breaking change as it may change the output bundle (increase in size).

Pull Request resolved: #972

Test Plan: All current tests should pass.

Reviewed By: motiz88

Differential Revision: D46591290

Pulled By: jacdebug

fbshipit-source-id: a94fcd635a9ac2d0d87ddd0bf3fe82f0c6436c82

packages/metro-config/src/__tests__/__snapshots__/loadConfig-test.js.snap

@@ -132,7 +132,6 @@ Object {
       },
       "output": Object {
         "ascii_only": true,
-        "comments": false,
         "quote_style": 3,
         "wrap_iife": true,
       },
@@ -311,7 +310,6 @@ Object {
       },
       "output": Object {
         "ascii_only": true,
-        "comments": false,
         "quote_style": 3,
         "wrap_iife": true,
       },
@@ -490,7 +488,6 @@ Object {
       },
       "output": Object {
         "ascii_only": true,
-        "comments": false,
         "quote_style": 3,
         "wrap_iife": true,
       },
@@ -669,7 +666,6 @@ Object {
       },
       "output": Object {
         "ascii_only": true,
-        "comments": false,
         "quote_style": 3,
         "wrap_iife": true,
       },

packages/metro-config/src/defaults/index.js

@@ -112,7 +112,6 @@ const getDefaultValues = (projectRoot: ?string): ConfigT => ({
       },
       output: {
         ascii_only: true,
-        comments: false,
         quote_style: 3,
         wrap_iife: true,
       },