use toMatchSnapshot instead of toMatchFormattedCss

More info: tailwindlabs#12170

Author: RobinMalfait

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

@@ -0,0 +1,9 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`should test the 'popoverOpenVariant' plugin 1`] = `
+"
+.popover-open\\:flex:popover-open {
+  display: flex;
+}
+"
+`;

tests/plugins/variants/popoverOpenVariant.test.js

@@ -1,7 +1,3 @@
-import { css, quickVariantPluginTest } from '../../util/run'
+import { quickVariantPluginTest } from '../../util/run'
 
-quickVariantPluginTest('popoverOpenVariant').toMatchFormattedCss(css`
-  .popover-open\:flex:popover-open {
-    display: flex;
-  }
-`)
+quickVariantPluginTest('popoverOpenVariant').toMatchSnapshot()