fix(deps): update dependency postcss-preset-env to ^6.0.8 (#4029)

This PR contains the following updates:

| Package | Type | Update | Change | References |
|---|---|---|---|---|
| postcss-preset-env | dependencies | patch | `^6.0.7` -> `^6.0.8` | [source](https://renovatebot.com/gh/csstools/postcss-preset-env) |

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### Release Notes

<details>
<summary>csstools/postcss-preset-env</summary>

### [`v6.0.8`](https://renovatebot.com/gh/csstools/postcss-preset-env/blob/master/CHANGELOG.md#&#8203;608-October-1-2018)

[Compare Source](7dfb8c9d7c...71ff1e5930)

-   Updated: `caniuse-lite` to 1.0.[`3000088`](https://renovatebot.com/gh/csstools/postcss-preset-env/commit/30000888) (patch)
-   Updated: `postcss` to 7.0.4 (patch)

**Did you hear? PostCSS Preset Env is now part of Create React App!** 🎉

</details>

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---

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package.json

@@ -109,7 +109,7 @@
     "postcss-import": "^12.0.0",
     "postcss-import-resolver": "^1.1.0",
     "postcss-loader": "^3.0.0",
-    "postcss-preset-env": "^6.0.7",
+    "postcss-preset-env": "^6.0.8",
     "postcss-url": "^8.0.0",
     "semver": "^5.5.1",
     "serialize-javascript": "^1.5.0",

packages/nuxt-legacy/package.json

@@ -95,7 +95,7 @@
     "postcss-import": "^12.0.0",
     "postcss-import-resolver": "^1.1.0",
     "postcss-loader": "^3.0.0",
-    "postcss-preset-env": "^6.0.7",
+    "postcss-preset-env": "^6.0.8",
     "postcss-url": "^8.0.0",
     "semver": "^5.5.1",
     "serialize-javascript": "^1.5.0",