chore: fix markdown example with overflowing content (vuejs#1410) [ci skip]

Author: Heroor

packages/vue/examples/classic/markdown.html

@@ -37,7 +37,8 @@
 
 textarea, #editor div {
   display: inline-block;
-  width: 49%;
+  overflow: auto;
+  width: 50%;
   height: 100%;
   vertical-align: top;
   -webkit-box-sizing: border-box;

packages/vue/examples/composition/markdown.html

@@ -36,7 +36,8 @@
 
 textarea, #editor div {
   display: inline-block;
-  width: 49%;
+  overflow: auto;
+  width: 50%;
   height: 100%;
   vertical-align: top;
   -webkit-box-sizing: border-box;