fix(gatsby): bump flex-bug postcss-plugin and postcss-loader (#21398)

packages/gatsby/package.json

@@ -108,8 +108,8 @@
     "parseurl": "^1.3.3",
     "physical-cpu-count": "^2.0.0",
     "pnp-webpack-plugin": "^1.5.0",
-    "postcss-flexbugs-fixes": "^3.3.1",
-    "postcss-loader": "^2.1.6",
+    "postcss-flexbugs-fixes": "^4.2.0",
+    "postcss-loader": "^3.0.0",
     "prompts": "^2.3.0",
     "prop-types": "^15.7.2",
     "raw-loader": "^0.5.1",

yarn.lock

@@ -17655,12 +17655,12 @@ postcss-discard-overridden@^4.0.1:
   dependencies:
     postcss "^7.0.0"
 
-postcss-flexbugs-fixes@^3.3.1:
-  version "3.3.1"
-  resolved "https://registry.yarnpkg.com/postcss-flexbugs-fixes/-/postcss-flexbugs-fixes-3.3.1.tgz#0783cc7212850ef707f97f8bc8b6fb624e00c75d"
-  integrity sha512-9y9kDDf2F9EjKX6x9ueNa5GARvsUbXw4ezH8vXItXHwKzljbu8awP7t5dCaabKYm18Vs1lo5bKQcnc0HkISt+w==
+postcss-flexbugs-fixes@^4.2.0:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/postcss-flexbugs-fixes/-/postcss-flexbugs-fixes-4.2.0.tgz#662b3dcb6354638b9213a55eed8913bcdc8d004a"
+  integrity sha512-QRE0n3hpkxxS/OGvzOa+PDuy4mh/Jg4o9ui22/ko5iGYOG3M5dfJabjnAZjTdh2G9F85c7Hv8hWcEDEKW/xceQ==
   dependencies:
-    postcss "^6.0.1"
+    postcss "^7.0.26"
 
 postcss-load-config@^2.0.0:
   version "2.0.0"
@@ -17669,16 +17669,6 @@ postcss-load-config@^2.0.0:
     cosmiconfig "^4.0.0"
     import-cwd "^2.0.0"
 
-postcss-loader@^2.1.6:
-  version "2.1.6"
-  resolved "https://registry.yarnpkg.com/postcss-loader/-/postcss-loader-2.1.6.tgz#1d7dd7b17c6ba234b9bed5af13e0bea40a42d740"
-  integrity sha512-hgiWSc13xVQAq25cVw80CH0l49ZKlAnU1hKPOdRrNj89bokRr/bZF2nT+hebPPF9c9xs8c3gw3Fr2nxtmXYnNg==
-  dependencies:
-    loader-utils "^1.1.0"
-    postcss "^6.0.0"
-    postcss-load-config "^2.0.0"
-    schema-utils "^0.4.0"
-
 postcss-loader@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/postcss-loader/-/postcss-loader-3.0.0.tgz#6b97943e47c72d845fa9e03f273773d4e8dd6c2d"
@@ -18017,6 +18007,15 @@ postcss@^7.0.23:
     source-map "^0.6.1"
     supports-color "^6.1.0"
 
+postcss@^7.0.26:
+  version "7.0.26"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-7.0.26.tgz#5ed615cfcab35ba9bbb82414a4fa88ea10429587"
+  integrity sha512-IY4oRjpXWYshuTDFxMVkJDtWIk2LhsTlu8bZnbEJA4+bYT16Lvpo8Qv6EvDumhYRgzjZl489pmsY3qVgJQ08nA==
+  dependencies:
+    chalk "^2.4.2"
+    source-map "^0.6.1"
+    supports-color "^6.1.0"
+
 potrace@^2.1.2:
   version "2.1.2"
   resolved "https://registry.yarnpkg.com/potrace/-/potrace-2.1.2.tgz#61473a326be1e734abac6d14d54e1880eed35471"
@@ -20022,7 +20021,7 @@ scheduler@^0.18.0:
     loose-envify "^1.1.0"
     object-assign "^4.1.1"
 
-schema-utils@^0.4.0, schema-utils@^0.4.5:
+schema-utils@^0.4.5:
   version "0.4.7"
   resolved "https://registry.yarnpkg.com/schema-utils/-/schema-utils-0.4.7.tgz#ba74f597d2be2ea880131746ee17d0a093c68187"
   dependencies: