fix: prevent RuntimeError when filtering financials in FinnHubUtils

[sjhddh]

Summary

Fix a bug in FinnHubUtils.get_basic_financials() that causes a RuntimeError when selected_columns is provided.

The Bug

The original code modified a dictionary while iterating over its keys:

for k in output_dict.keys():
    if selected_columns and k not in selected_columns:
        output_dict.pop(k)  # RuntimeError: dictionary changed size during iteration

The Fix

Replace the problematic loop with a dict comprehension that creates a new filtered dictionary:

if selected_columns:
    output_dict = {k: v for k, v in output_dict.items() if k in selected_columns}

Test plan

• Verify the fix compiles without syntax errors
• Test FinnHubUtils.get_basic_financials("AAPL", selected_columns=["eps", "pe"]) no longer crashes