Fix incorrect formatting of multipleOf in error message

- `%d` casts the multipleOf to a whole number even if its a float with decimals
- `%f` would add unnecessary decimals, e.g. `0.01` would become `0.010000`
- `%s` maintains the same number of decimals, e.g. `0.01` stays `0.01`

Author: bertramakers

src/Schema/Type/Number.php

@@ -59,7 +59,7 @@ public function validate(mixed $value, callable $fail): void
             $this->multipleOf !== null &&
             (float) ($value / $this->multipleOf) !== round($value / $this->multipleOf)
         ) {
-            $fail(sprintf('must be a multiple of %d', $this->multipleOf));
+            $fail(sprintf('must be a multiple of %s', $this->multipleOf));
         }
     }