Fix a small typo in Gemmini matmul schedule

[codecov[bot]]

Codecov Report

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

Project coverage is 86.80%. Comparing base (1c31058) to head (1b1eb81). Report is 1 commits behind head on main.

:exclamation: Current head 1b1eb81 differs from pull request most recent head 4a5e247

Please upload reports for the commit 4a5e247 to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #665 +/- ## ======================================= Coverage 86.80% 86.80% ======================================= Files 91 91 Lines 21599 21599 ======================================= Hits 18749 18749 Misses 2850 2850 ```

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