refactor: remove unnecessary judgment (#8493)

Author: linjiajian999

src/compiler/parser/html-parser.js

@@ -248,12 +248,9 @@ export function parseHTML (html, options) {
     if (start == null) start = index
     if (end == null) end = index
 
-    if (tagName) {
-      lowerCasedTagName = tagName.toLowerCase()
-    }
-
     // Find the closest opened tag of the same type
     if (tagName) {
+      lowerCasedTagName = tagName.toLowerCase()
       for (pos = stack.length - 1; pos >= 0; pos--) {
         if (stack[pos].lowerCasedTag === lowerCasedTagName) {
           break