chore: add deprecation flag on base upload flow route

[jordanrfrazier]

Adds deprecated flag to an old route that I believe is superseded by more specific upload routes like https://github.com/langflow-ai/langflow/blob/deprecate-upload-route/src/backend/base/langflow/api/v1/files.py#L40

[ogabrielluiz]

LGTM

[codspeed-hq]

CodSpeed Performance Report

Merging #4717 will degrade performances by 95.88%

_{Comparing deprecate-upload-route (1268592) with main (25a0d76)}

Summary

⚡ 1 improvements
❌ 2 regressions
✅ 12 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	deprecate-upload-route	Change
⚡	test_successful_run_with_input_type_any	297.8 ms	218.9 ms	+36.03%
❌	test_successful_run_with_output_type_any	219.5 ms	5,326.2 ms	-95.88%
❌	test_successful_run_with_output_type_debug	138.8 ms	295.3 ms	-53%