Fix clippy lint about read_write_image_impl
Fix clippy lint about read_write_image_impl

mindriot101/rust-fitsio,mindriot101/rust-fitsio,mindriot101/rust-fitsio,mindriot101/rust-cfitsio,mindriot101/rust-cfitsio,mindriot101/rust-fitsio,mindriot101/rust-fitsio