Remove empty leading cell from Lab 06 Prompt Engineering notebook

[Copilot]

Lab 06 - Prompt Engineering/Prompt Engineering.ipynb had a spurious empty code cell as its first cell, causing the notebook to open with a blank cell before any content.

Change

• Removed the empty code cell at index 0; notebook now opens directly on the ### Prompt Engineering markdown cell.

Original prompt

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This section details on the original issue you should resolve

<issue_title>WorkshopPLUS- Azure AI: Platform and Services | Lab06 - Remove Notebook empty cell</issue_title>
<issue_description>"Lab 06 - Prompt Engineering/Prompt Engineering.ipynb" starts with an empty cell. Remove it.</issue_description>

<agent_instructions>Use "Bug756667" in the branch name. Leave the PR in draft mode.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes WorkshopPLUS- Azure AI: Platform and Services | Lab06 - Remove Notebook empty cell #56

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[omarv74]

Looks good