Log Message:
(graphics/R-isoband) Updated 0.2.4 to 0.2.7, make test passed

# isoband 0.2.7

- Remove compile-time dependency on testthat.

- Changed maintainer after the original author (Claus Wilke) donated codebase
  to r-lib.

isoband 0.2.6
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- Update to the latest testthat headers for compatibility with
  LLVM clang 15.0.0.

- Correct label angle for current aspect ratio in `isolines_grob()`
  (#28, @eliocamp).

isoband 0.2.5
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- Add a new label placer function `label_placer_middle()`
  (#24, @jamarav).

- The vendored testthat/catch code now uses a constant
  value for the stack size rather than relying on `SIGSTKSZ`.
  See: https://github.com/r-lib/testthat/issues/1373