Python: set openai package to newer version and removed default value of parallel tool calls

[eavanvalkenburg]

Motivation and Context

We noticed that the openai package dependency spec was off and did not update that when present to the newest version, fixed now.
Also we mistakenly had a default value for parallel_tool_calls in our prompt executions settings, as with other settings we do not maintain a default value if the API has a default and in this case having that parameter when calling a reasoning model threw an error, fixed here.

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/connectors/ai/open_ai/prompt_execution_settings
open_ai_prompt_execution_settings.py	84	2	98%	119, 133
TOTAL	18530	2169	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3174	4 💤	0 ❌	0 🔥	1m 42s ⏱️