drop custom namespace

Author: joephela

packages/eslint-config-widen-emotion/src/index.ts

@@ -2,6 +2,6 @@ import noConditionalCssProp from './rules/no-conditional-css-prop.js'
 
 export default {
   rules: {
-    'custom/no-conditional-css-prop': noConditionalCssProp,
+    'no-conditional-css-prop': noConditionalCssProp,
   },
 }