Use 'div_ceil' to make clippy happy

[steschu77]

• Fixes CI clippy warnings about reimplementing div_ceil
• Should make CI green again

[fintelia]

Thanks!

[Shnatsel]

I hope this didn't regress performance. Applying similar transformations suggested by Clippy had caused significant performance regressions in the past, for example

image-webp/src/vp8.rs

Lines 994 to 999 in 93baf7d

	// Clippy suggests the clamp method, but it seems to optimize worse as of rustc 1.82.0 nightly.
	#[allow(clippy::manual_clamp)]
	fn clip(v: i32) -> u8 {
	const YUV_FIX2: i32 = 6;
	(v >> YUV_FIX2).max(0).min(255) as u8
	}

[Shnatsel]

On second look, none of these calculations are in hot loops, so performance should be unchanged.