replace tab with 4 spaces

Author: bytesnail

src/builder.rs

@@ -667,11 +667,11 @@ impl Builder {
     /// if the leftmost bit was one.
     ///
     /// ```rust,no_run
-	/// //fix doc error about overflowing_literals
-	/// //rendered rfc: https://github.com/rust-lang/rfcs/blob/master/text/2438-deny-integer-literal-overflow-lint.md
-	/// //tracking issue: https://github.com/rust-lang/rust/issues/54502
-	/// #![allow(overflowing_literals)]
-	///
+    /// //fix doc error about overflowing_literals
+    /// //rendered rfc: https://github.com/rust-lang/rfcs/blob/master/text/2438-deny-integer-literal-overflow-lint.md
+    /// //tracking issue: https://github.com/rust-lang/rust/issues/54502
+    /// #![allow(overflowing_literals)]
+    ///
     /// // Logical Right Shift
     /// assert_eq!(0b1100_0000 >> 2, 0b0011_0000);
     /// assert_eq!(0b0000_0010 >> 1, 0b0000_0001);