Revert "feat: add new css parser - postcss (#1458)"

This reverts commit 89ae4d2.

This feature was found to cause problems with parsing some CSS.

Author: Vadman97

packages/rrweb-snapshot/package.json

@@ -66,8 +66,5 @@
     "vite": "^5.3.1",
     "vite-plugin-dts": "^3.9.1",
     "vitest": "^1.4.0"
-  },
-  "dependencies": {
-    "postcss": "^8.4.38"
   }
 }