chore: update code comment (vuejs#1860)

Author: jayconscious

lib/plugin-webpack4.js

@@ -69,7 +69,7 @@ class VueLoaderPlugin {
     vueLoaderUse.ident = 'vue-loader-options'
     vueLoaderUse.options = vueLoaderUse.options || {}
 
-    // for each user rule (expect the vue rule), create a cloned rule
+    // for each user rule (except the vue rule), create a cloned rule
     // that targets the corresponding language blocks in *.vue files.
     const clonedRules = rules
       .filter(r => r !== vueRule)