[BUG] Fix header name in swagger response

- This was incorrectly copied from the `swaggerCommitList` struct, which
on the other hand does set `X-Total`, but the API handler that uses this
response only sets `X-Total-Count`.

routers/api/v1/swagger/repo.go

@@ -263,7 +263,7 @@ type swaggerChangedFileList struct {
 	PerPage int `json:"X-PerPage"`
 
 	// Total commit count
-	Total int `json:"X-Total"`
+	Total int `json:"X-Total-Count"`
 
 	// Total number of pages
 	PageCount int `json:"X-PageCount"`