update postcss version

dashboard/yarn.lock

@@ -2221,7 +2221,7 @@ postcss@^5.2.17:
     source-map "^0.5.6"
     supports-color "^3.2.3"
 
-postcss@^8.1.10, postcss@^8.4.12:
+postcss@^8.1.10:
   version "8.4.12"
   resolved "https://registry.npmmirror.com/postcss/-/postcss-8.4.12.tgz"
   integrity sha512-lg6eITwYe9v6Hr5CncVbK70SoioNQIq81nsaG86ev5hAidQvmOeETBqs7jm43K2F5/Ley3ytDtriImV6TpNiSg==
@@ -2230,6 +2230,15 @@ postcss@^8.1.10, postcss@^8.4.12:
     picocolors "^1.0.0"
     source-map-js "^1.0.2"
 
+postcss@^8.4.12:
+  version "8.4.12"
+  resolved "https://registry.npmmirror.com/postcss/-/postcss-8.4.12.tgz#1e7de78733b28970fa4743f7da6f3763648b1905"
+  integrity sha512-lg6eITwYe9v6Hr5CncVbK70SoioNQIq81nsaG86ev5hAidQvmOeETBqs7jm43K2F5/Ley3ytDtriImV6TpNiSg==
+  dependencies:
+    nanoid "^3.3.1"
+    picocolors "^1.0.0"
+    source-map-js "^1.0.2"
+
 posthtml-parser@^0.2.0, posthtml-parser@^0.2.1:
   version "0.2.1"
   resolved "https://registry.npmmirror.com/posthtml-parser/-/posthtml-parser-0.2.1.tgz#35d530de386740c2ba24ff2eb2faf39ccdf271dd"