Make branch icon stand out more (go-gitea#20726)

- Backport go-gitea#20726
  - Currently the branch icon is "squashed" between the two branch names and feels a bit "amateur-ish" to my feeling(relative to other UI elements).
  - This patch tries to improve that by making the icon bigger and by adding some margin to not have a "squashed" icon.
  - This patch also includes a "fix", for some reason this symbol is not centering correctly. So apply allign-items: center to the top div

templates/shared/issuelist.tmpl

@@ -60,19 +60,17 @@
 						{{$.i18n.Tr .GetLastEventLabelFake $timeStr (.Poster.GetDisplayName | Escape) | Safe}}
 					{{end}}
 					{{if .IsPull}}
-						<div class="branches">
+						<div class="branches df ac">
 							<div class="branch">
-								<a class="bold" href="{{.PullRequest.BaseRepo.HTMLURL}}/src/branch/{{PathEscapeSegments .PullRequest.BaseBranch}}">
+								<a href="{{.PullRequest.BaseRepo.HTMLURL}}/src/branch/{{PathEscapeSegments .PullRequest.BaseBranch}}">
 									{{/* inline to remove the spaces between spans */}}
 									{{if ne .RepoID .PullRequest.BaseRepoID}}<span class="truncated-name">{{.PullRequest.BaseRepo.OwnerName}}</span>:{{end}}<span class="truncated-name">{{.PullRequest.BaseBranch}}</span>
 								</a>
 							</div>
-
-							&laquo;
-
+							{{svg "gitea-double-chevron-left" 12 "mx-1"}}
 							{{if .PullRequest.HeadRepo}}
 							<div class="branch">
-								<a class="bold" href="{{.PullRequest.HeadRepo.HTMLURL}}/src/branch/{{PathEscapeSegments .PullRequest.HeadBranch}}">
+								<a href="{{.PullRequest.HeadRepo.HTMLURL}}/src/branch/{{PathEscapeSegments .PullRequest.HeadBranch}}">
 									{{/* inline to remove the spaces between spans */}}
 									{{if ne .RepoID .PullRequest.HeadRepoID}}<span class="truncated-name">{{.PullRequest.HeadRepo.OwnerName}}</span>:{{end}}<span class="truncated-name">{{.PullRequest.HeadBranch}}</span>
 								</a>

web_src/less/shared/issuelist.less

@@ -122,7 +122,7 @@
 
   .branches {
     display: inline-flex;
-    padding: 0 6px;
+    padding: 0 4px;
 
     .branch {
       background-color: var(--color-secondary);