修正 lecture-6 两处错别字

[siuis]

修正 lecture-6 两处错别字

[CLAassistant]

All committers have signed the CLA.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (0ec922e) 36.99% compared to head (acd8246) 36.99%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #342 +/- ## ======================================= Coverage 36.99% 36.99% ======================================= Files 101 101 Lines 7272 7272 ======================================= Hits 2690 2690 Misses 4582 4582 ```

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[hnwyllmm]

@siuis 请签署一下CLA

[siuis]

@siuis 请签署一下CLA

@hnwyllmm 👌