Fix issue #5946: changed code for ACASessionsExecutor _ensure_access_token to be https:/ /dynamicsessions.io/.default

[EdwinInnovation]

Why are these changes needed?

when I want to create a ACASessionsExecutor instance and execute some code, the default library imported does not work. It always returns: "ClientAuthenticationError: Authentication failed: AADSTS70011: The provided request must include a 'scope' input parameter. The provided value for the input parameter 'scope' is not valid. The scope https://dynamicsessions.io/ is not valid. Trace ID: d75efa58-8be7-44ef-8839-aacfdc850600 Correlation ID: a8e4d859-92da-4fbe-a8e0-05116323ab55 Timestamp: 2025-03-14 14:15:09Z"

After changing the scope in _ensure_access_token to be "https://dynamicsessions.io/.default" rather than ""https://dynamicsessions.io/" and it worked.

Related issue number

issue #5946

Checks

• [Y ] I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• [ Y] I've made sure all auto checks have passed.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.73%. Comparing base (9103359) to head (6ad0475).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
..._executors/azure/_azure_container_code_executor.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6001   +/-   ##
=======================================
  Coverage   76.73%   76.73%           
=======================================
  Files         191      191           
  Lines       13170    13170           
=======================================
  Hits        10106    10106           
  Misses       3064     3064           

Flag	Coverage Δ
unittests	76.73% <0.00%> (ø)

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[EdwinInnovation]

@ekzhu Could you please review this PR?