Use .contains instead of manual reimplementation.

It's also significantly easier to read.

library/core/src/num/mod.rs

@@ -847,7 +847,7 @@ fn from_str_radix<T: FromStrRadixHelper>(src: &str, radix: u32) -> Result<T, Par
     use self::ParseIntError as PIE;
 
     assert!(
-        radix >= 2 && radix <= 36,
+        (2..=36).contains(&radix),
         "from_str_radix_int: must lie in the range `[2, 36]` - found {}",
         radix
     );