Fix dropdown icon layout on diff page (go-gitea#25397)

Address
go-gitea#25163 (comment)

Remove the unused  "icon-button".

And fix the layout:

Without the dropdown icon:

```
	{{svg "gitea-whitespace"}}
```


![image](https://github.com/go-gitea/gitea/assets/2114189/58a524ba-f289-4982-aea2-6f9f9f9cbdcf)


With the dropdown icon:

```
	{{svg "gitea-whitespace" 16 "gt-mr-3"}}
	{{svg "octicon-triangle-down" 14 "dropdown icon"}}
```


![image](https://github.com/go-gitea/gitea/assets/2114189/eb99168b-5d49-40a7-8665-5296cbb4e486)

Author: wxiaoguang

templates/package/shared/cleanup_rules/list.tmpl

@@ -9,7 +9,7 @@
 		{{range .CleanupRules}}
 			<div class="item">
 				<div class="right floated content">
-					<div class="ui dropdown tiny basic button icon-button">
+					<div class="ui dropdown tiny basic button">
 						{{svg "octicon-kebab-horizontal"}}
 						<div class="menu">
 							<a class="item" href="{{$.Link}}/rules/{{.ID}}">{{$.locale.Tr "edit"}}</a>

templates/repo/diff/new_review.tmpl

@@ -1,5 +1,5 @@
 <div id="review-box">
-	<button class="ui tiny green button gt-ml-2 gt-mr-0 js-btn-review">
+	<button class="ui tiny green button gt-pr-2 gt-df js-btn-review">
 		{{.locale.Tr "repo.diff.review"}}
 		<span class="ui small label review-comments-counter" data-pending-comment-number="{{.PendingCodeCommentNumber}}">{{.PendingCodeCommentNumber}}</span>
 		{{svg "octicon-triangle-down" 14 "dropdown icon"}}

templates/repo/diff/options_dropdown.tmpl

@@ -1,4 +1,4 @@
-<div class="ui dropdown tiny basic button icon-button" data-tooltip-content="{{.locale.Tr "repo.diff.options_button"}}">
+<div class="ui dropdown tiny basic button" data-tooltip-content="{{.locale.Tr "repo.diff.options_button"}}">
 	{{svg "octicon-kebab-horizontal"}}
 	<div class="menu">
 		<a class="item" id="show-file-list-btn">{{.locale.Tr "repo.diff.show_diff_stats"}}</a>

templates/repo/diff/whitespace_dropdown.tmpl

@@ -1,6 +1,5 @@
-<div class="ui dropdown tiny basic button icon-button" data-tooltip-content="{{.locale.Tr "repo.diff.whitespace_button"}}">
+<div class="ui dropdown tiny basic button" data-tooltip-content="{{.locale.Tr "repo.diff.whitespace_button"}}">
 	{{svg "gitea-whitespace"}}
-	{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 	<div class="menu">
 		<a class="item" href="?style={{if .IsSplitStyle}}split{{else}}unified{{end}}&whitespace=show-all">
 			<label class="gt-pointer-events-none">
@@ -28,4 +27,4 @@
 		</a>
 	</div>
 </div>
-<a class="ui tiny basic button icon-button" href="?style={{if .IsSplitStyle}}unified{{else}}split{{end}}&whitespace={{$.WhitespaceBehavior}}" data-tooltip-content="{{if .IsSplitStyle}}{{.locale.Tr "repo.diff.show_unified_view"}}{{else}}{{.locale.Tr "repo.diff.show_split_view"}}{{end}}">{{if .IsSplitStyle}}{{svg "gitea-join"}}{{else}}{{svg "gitea-split"}}{{end}}</a>
+<a class="ui tiny basic button" href="?style={{if .IsSplitStyle}}unified{{else}}split{{end}}&whitespace={{$.WhitespaceBehavior}}" data-tooltip-content="{{if .IsSplitStyle}}{{.locale.Tr "repo.diff.show_unified_view"}}{{else}}{{.locale.Tr "repo.diff.show_split_view"}}{{end}}">{{if .IsSplitStyle}}{{svg "gitea-join"}}{{else}}{{svg "gitea-split"}}{{end}}</a>

web_src/css/modules/button.css

@@ -29,12 +29,6 @@
   color: var(--color-red);
 }
 
-/* try to match button with no icons in height */
-.icon-button {
-  padding-top: 7.42px !important;
-  padding-bottom: 7.42px !important;
-}
-
 /* btn is a plain button without any opinionated styling */
 
 .btn {

web_src/css/repo.css

@@ -1666,8 +1666,9 @@
   background-color: var(--color-teal);
 }
 
-.repository .diff-detail-box .button {
-  padding: 8px 12px;
+.repository .diff-detail-box .ui.button {
+  padding: 0 12px;
+  height: 30px;
 }
 
 .repository .diff-box .header:not(.resolved-placeholder) {