Fix for 16f min (#3913)

Co-authored-by: Peter McNeeley <[email protected]>

src/webgpu/shader/validation/expression/matrix/add_sub.spec.ts

@@ -275,7 +275,7 @@ g.test('underflow_f16')
     let rhs = `mat${t.params.c}x${t.params.r}h(`;
     for (let i = 0; i < t.params.c; i++) {
       for (let k = 0; k < t.params.r; k++) {
-        lhs += `${kValue.f32.negative.min / 2},`;
+        lhs += `${kValue.f16.negative.min / 2},`;
         rhs += `${t.params.rhs},`;
       }
     }