docs: fix typo `bin/active` → `bin/activate` in tutorial (#25473)

## Summary

Fixes a one-character typo in  (line 61).

The Linux/macOS virtual environment activation command was written as:

```
source .venv/bin/active
```

but should be:

```
source .venv/bin/activate
```

The Windows command on the same line () was already correct, making the
discrepancy easy to spot.

## How verified

The fix was verified by reading the file directly — is not a valid shell
script; the correct file installed by Python’s `venv` module is always .

Co-authored-by: Claude <noreply@anthropic.com>