Satisfy clippy on the reference tone curve's data

One sample of the ACR3 table is 0.70711, which clippy reads as an
approximation of 1/sqrt(2). It is the curve's published value, so the
lint is allowed on the table with that reason rather than the number
replaced. And the pair-count check uses is_multiple_of.

core/dr-types/src/tone.rs

@@ -21,7 +21,12 @@
 pub const TONE_SAMPLES: usize = 1025;
 
 /// The ACR3 default tone curve, linear in, linear out.
+///
+/// `approx_constant` is allowed because one sample is 0.70711, which clippy
+/// takes for an approximation of 1/√2. It is a measured value of the curve,
+/// copied as published; replacing it with the constant would change it.
 #[rustfmt::skip]
+#[allow(clippy::approx_constant)]
 pub const ACR3_DEFAULT: [f32; TONE_SAMPLES] = [
     0.00000, 0.00078, 0.00160, 0.00242, 0.00314, 0.00385, 0.00460, 0.00539,
     0.00623, 0.00712, 0.00806, 0.00906, 0.01012, 0.01122, 0.01238, 0.01359,
@@ -163,7 +168,7 @@ pub const ACR3_DEFAULT: [f32; TONE_SAMPLES] = [
 /// x not increasing, values outside `[0, 1]`) or describe the identity,
 /// which RawTherapee also treats as no curve.
 pub fn resample_tone_curve(pairs: &[f32]) -> Option<Vec<f32>> {
-    if pairs.len() < 4 || pairs.len() % 2 != 0 {
+    if pairs.len() < 4 || !pairs.len().is_multiple_of(2) {
         return None;
     }
     let xs: Vec<f64> = pairs.iter().step_by(2).map(|&v| f64::from(v)).collect();