Remove unnecessary inline style for tab-size (#31224)

Move the rule to the parent node. `tab-size` is inherited so will work
just as before.

(cherry picked from commit 0f0db6a14fd10a493ba73f211e2e627c3884d114)

routers/web/repo/issue_content_history.go

@@ -158,7 +158,7 @@ func GetContentHistoryDetail(ctx *context.Context) {
 
 	// use chroma to render the diff html
 	diffHTMLBuf := bytes.Buffer{}
-	diffHTMLBuf.WriteString("<pre class='chroma' style='tab-size: 4'>")
+	diffHTMLBuf.WriteString("<pre class='chroma'>")
 	for _, it := range diff {
 		if it.Type == diffmatchpatch.DiffInsert {
 			diffHTMLBuf.WriteString("<span class='gi'>")

web_src/css/repo.css

@@ -2489,6 +2489,7 @@ tbody.commit-list {
   min-height: 12em;
   max-height: calc(100vh - 10.5rem);
   overflow-y: auto;
+  tab-size: 4;
 }
 
 .comment-diff-data pre {