chore(deps): update dependency postcss to ^8.1.4 (#27534)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

packages/gatsby-plugin-image/package.json

@@ -63,7 +63,7 @@
  "do-sync": "^2.2.0",
  "microbundle": "^0.12.3",
  "npm-run-all": "^4.1.5",
- "postcss": "^8.1.1",
+ "postcss": "^8.1.4",
  "terser": "^5.3.3",
  "typescript": "^3.9.5"
  },

yarn.lock

@@ -16953,10 +16953,10 @@ nan@^2.10.0, nan@^2.9.2:
  resolved "https://registry.yarnpkg.com/nan/-/nan-2.14.0.tgz#7818f722027b2459a86f0295d434d1fc2336c52c"
  integrity sha512-INOFj37C7k3AfaNTtX8RhsTw7qRy7eLET14cROi9+5HAVbbHuIWUHEauBv5qT4Av2tWasiTY1Jw6puUNqRJXQg==
 
-nanoid@^3.1.12:
- version "3.1.12"
- resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.1.12.tgz#6f7736c62e8d39421601e4a0c77623a97ea69654"
- integrity sha512-1qstj9z5+x491jfiC4Nelk+f8XBad7LN20PmyWINJEMRSf3wcAjAWysw1qaA8z6NSKe2sjq1hRSDpBH5paCb6A==
+nanoid@^3.1.15:
+ version "3.1.15"
+ resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.1.15.tgz#28e7c4ce56aff2d0c2d37814c7aef9d6c5b3e6f3"
+ integrity sha512-n8rXUZ8UU3lV6+43atPrSizqzh25n1/f00Wx1sCiE7R1sSHytZLTTiQl8DjC4IDLOnEZDlgJhy0yO4VsIpMxow==
 
 nanomatch@^1.2.9:
  version "1.2.13"
@@ -19179,14 +19179,14 @@ postcss@^7.0.0, postcss@^7.0.1, postcss@^7.0.14, postcss@^7.0.17, postcss@^7.0.1
  source-map "^0.6.1"
  supports-color "^6.1.0"
 
-postcss@^8.1.1:
- version "8.1.1"
- resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.1.1.tgz#c3a287dd10e4f6c84cb3791052b96a5d859c9389"
- integrity sha512-9DGLSsjooH3kSNjTZUOt2eIj2ZTW0VI2PZ/3My+8TC7KIbH2OKwUlISfDsf63EP4aiRUt3XkEWMWvyJHvJelEg==
+postcss@^8.1.4:
+ version "8.1.4"
+ resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.1.4.tgz#356dfef367a70f3d04347f74560c85846e20e4c1"
+ integrity sha512-LfqcwgMq9LOd8pX7K2+r2HPitlIGC5p6PoZhVELlqhh2YGDVcXKpkCseqan73Hrdik6nBd2OvoDPUaP/oMj9hQ==
  dependencies:
  colorette "^1.2.1"
  line-column "^1.0.2"
- nanoid "^3.1.12"
+ nanoid "^3.1.15"
  source-map "^0.6.1"
 
 potrace@^2.1.8: