fix: Ensure the service selection comes before the choice

[erichare]

This pull request is a quick hotfix to the Vector RAG starter template, just to ensure the component order matches the Astra DB Vector Store component order.

[codspeed-hq]

CodSpeed Performance Report

Merging #4692 will degrade performances by 36.09%

_{Comparing fix-astradb-input-order (62cece8) with main (2fa2580)}

Summary

⚡ 1 improvements
❌ 2 regressions
✅ 12 untouched benchmarks

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

Benchmarks breakdown

	Benchmark	main	fix-astradb-input-order	Change
⚡	test_load_flows	2.2 ms	1.3 ms	+72.99%
❌	test_successful_run_with_input_type_text	140.7 ms	218.9 ms	-35.74%
❌	test_successful_run_with_output_type_debug	139.1 ms	217.7 ms	-36.09%