docs: fix duplicate words in documentation

[chenlichao]

Why are these changes needed?

Fixes three duplicated words in documentation and sample setup instructions:

• MUST be be → MUST be
• in the the same directory → in the same directory
• such as the the tool call → such as the tool call

These are small documentation/readability fixes only; no code behavior changes.

Related issue number

N/A

Checks

• 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. (Not relevant; documentation-only typo fixes.)
• I've made sure all auto checks have passed. (git diff --check)

[chenlichao]

@microsoft-github-policy-service agree