use toMatchSnapshot instead of toMatchFormattedCss

More info: tailwindlabs#12170

Author: RobinMalfait

tests/plugins/variants/__snapshots__/startingStyleVariant.test.js.snap

@@ -0,0 +1,11 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`should test the 'startingStyleVariant' plugin 1`] = `
+"
+@starting-style {
+  .starting\\:flex {
+    display: flex;
+  }
+}
+"
+`;

tests/plugins/variants/startingStyleVariant.test.js

@@ -1,9 +1,3 @@
-import { css, quickVariantPluginTest } from '../../util/run'
+import { quickVariantPluginTest } from '../../util/run'
 
-quickVariantPluginTest('startingStyleVariant').toMatchFormattedCss(css`
-  @starting-style {
-    .starting\:flex {
-      display: flex;
-    }
-  }
-`)
+quickVariantPluginTest('startingStyleVariant').toMatchSnapshot()