make a f32::gamma test pass

Author: LorrensP-2158466

library/std/tests/floats/f32.rs

@@ -196,7 +196,7 @@ fn test_gamma() {
     assert_approx_eq!(1.0f32.gamma(), 1.0f32);
     assert_approx_eq!(2.0f32.gamma(), 1.0f32);
     assert_approx_eq!(3.0f32.gamma(), 2.0f32);
-    assert_approx_eq!(4.0f32.gamma(), 6.0f32);
+    assert_approx_eq!(4.0f32.gamma(), 6.0f32, APPROX_DELTA);
     assert_approx_eq!(5.0f32.gamma(), 24.0f32, APPROX_DELTA);
     assert_approx_eq!(0.5f32.gamma(), consts::PI.sqrt());
     assert_approx_eq!((-0.5f32).gamma(), -2.0 * consts::PI.sqrt());