README figure fix

[sigmafelix]

• rlang::check_install just loads but does not attach packages
• Functions are explicitly called with ::
• Redundant figures are removed

[codecov[bot]]

Codecov Report

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

Comparison is base (50031b1) 99.17% compared to head (d64bc76) 99.17%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #54 +/- ## ======================================= Coverage 99.17% 99.17% ======================================= Files 5 5 Lines 603 603 ======================================= Hits 598 598 Misses 5 5 ```

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