feat!: rename GazeDataFrame.copy() to clone()

[dkrako]

We discussed this already in November when I added this function, but I forgot to do this apparently.

I guess nobody started to use this method in the meantime, so I would just rename it without deprecation

[codecov[bot]]

Codecov Report

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

Comparison is base (3b43886) 100.00% compared to head (f033570) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #657 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 54 54 Lines 2357 2357 Branches 588 588 ========================================= Hits 2357 2357 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.