fix: use WaitGroup.Go() for modernize linter

Replace wg.Add(1)/go func()/defer wg.Done() pattern with
the simpler wg.Go() method as required by the modernize linter.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/gitea-cli/cmd/upload.go

@@ -367,9 +367,7 @@ func uploadChunks(ctx context.Context, server, token string, session *UploadSess
 
 	// Start workers
 	for range parallel {
-		wg.Add(1)
-		go func() { //nolint:modernize // Using separate error channel for first-error semantics
-			defer wg.Done()
+		wg.Go(func() {
 			for job := range jobs {
 				err := uploadChunk(server, token, session.ID, job.number, job.data)
 				if err != nil {
@@ -378,7 +376,7 @@ func uploadChunks(ctx context.Context, server, token string, session *UploadSess
 				}
 				tracker.Add(int64(len(job.data)))
 			}
-		}()
+		})
 	}
 
 	// Progress display