fix: address styling issues with empty lines in code blocks (#5140)

#### What type of PR is this?

/kind bug

#### What this PR does / why we need it:

修改 code 内`br` 标签的 `display`，用于适配 firefox 浏览器

#### How to test it?

测试在 firefox 浏览器下，使用代码块回车等是否会出现样式问题。

#### Which issue(s) this PR fixes:

Fixes #5064 

#### Does this PR introduce a user-facing change?
```release-note
解决在 Firefox 浏览器下的代码块编辑问题。
```

console/packages/editor/src/styles/base.scss

@@ -72,7 +72,7 @@
       }
 
       code br {
-        display: block;
+        display: initial;
       }
     }
   }