build(deps): bump postcss from 7.0.39 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 7.0.39 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@7.0.39...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -63,7 +63,7 @@
     "j-component": "^1.4.9",
     "less": "^3.10.3",
     "miniprogram-compiler": "latest",
-    "postcss": "^7.0.23",
+    "postcss": "^8.4.31",
     "pretty-format": "^26.0.1"
   }
 }