Fix max width and margin of comment box on conversation page (#24809)

Fix regression from #23937

The changes should only be limited to `.conversation-holder
.comment-code-cloud`, otherwise it will affect the `.comment-code-cloud`
in conversation tab

Before:

<img width="962" alt="Screen Shot 2023-05-19 at 18 22 25"
src="https://github.com/go-gitea/gitea/assets/17645053/0db01d04-2581-48f9-b46c-497836b1f12b">

After:

<img width="997" alt="Screen Shot 2023-05-19 at 18 35 01"
src="https://github.com/go-gitea/gitea/assets/17645053/5d14b67b-88c1-46c6-b859-fd41752b3ebb">

---------

Co-authored-by: Giteabot <[email protected]>

Author: HesterG

web_src/css/review.css

@@ -61,6 +61,9 @@
 .comment-code-cloud {
   padding: 0.5rem 1rem !important;
   position: relative;
+}
+
+.conversation-holder .comment-code-cloud {
   max-width: 820px;
 }