Hide `add file` button for pull mirrors (#25748)

I think hiding the add file button for mirror repositories that can keep the ui clean.

Before:

![image](https://github.com/go-gitea/gitea/assets/89133723/84ecf1a5-1a92-4bb1-b472-b4988a4441a9)

After:

![image](https://github.com/go-gitea/gitea/assets/89133723/95382e73-286b-4114-9997-456ed77e07ca)

templates/repo/home.tmpl

@@ -83,7 +83,7 @@
 					<a href="{{.Repository.Link}}/find/{{.BranchNameSubURL}}" class="ui compact basic button">{{.locale.Tr "repo.find_file.go_to_file"}}</a>
 				{{end}}
 
-				{{if and .CanWriteCode .IsViewBranch (not .Repository.IsArchived) (not .IsViewFile)}}
+				{{if and .CanWriteCode .IsViewBranch (not .Repository.IsMirror) (not .Repository.IsArchived) (not .IsViewFile)}}
 					<button class="ui dropdown basic compact jump button gt-mr-2"{{if not .Repository.CanEnableEditor}} disabled{{end}}>
 						{{.locale.Tr "repo.editor.add_file"}}
 						{{svg "octicon-triangle-down" 14 "dropdown icon"}}