Fixed Xyza to Laba color conversion. (#20728)

# Objective

Fixes `Xyza` to `Laba` color conversion.

As the website referenced in comment:

<img width="236" height="77" alt="image"
src="https://github.com/user-attachments/assets/aad9676a-33f5-428e-be8d-b25f2eb3b7f0"
/>

The variable that used to compares to `epsilon` is `zr`, but in actual
code, it's mistyped into `yr`.

## Solution

Changed `yr` to `zr`.

Author: 443eb9

crates/bevy_color/src/laba.rs

@@ -275,7 +275,7 @@ impl From<Xyza> for Laba {
         } else {
             (Laba::CIE_KAPPA * yr + 16.0) / 116.0
         };
-        let fz = if yr > Laba::CIE_EPSILON {
+        let fz = if zr > Laba::CIE_EPSILON {
             ops::cbrt(zr)
         } else {
             (Laba::CIE_KAPPA * zr + 16.0) / 116.0