Fix HTTP headers for issue attachment download

- Download filename was wrong for files other than images. Example: It was `download` instead of `file.pdf`
- PDF was downloading instead of showing on browser

cmd/web.go

@@ -336,11 +336,7 @@ func runWeb(ctx *cli.Context) error {
 			}
 			defer fr.Close()
 
-			ctx.Header().Set("Cache-Control", "public,max-age=86400")
-			ctx.Header().Set("Content-Disposition", fmt.Sprintf(`inline; filename="%s"`, attach.Name))
-			// Fix #312. Attachments with , in their name are not handled correctly by Google Chrome.
-			// We must put the name in " manually.
-			if err = repo.ServeData(ctx, "\""+attach.Name+"\"", fr); err != nil {
+			if err = repo.ServeData(ctx, attach.Name, fr); err != nil {
 				ctx.Handle(500, "ServeData", err)
 				return
 			}