replace | with || in {unsigned_int}::borrowing_sub

Using short-circuiting operators makes it easier to perform some kinds
of source code analysis, like MC/DC code coverage (a requirement in
safety-critical environments). The optimized x86_64 assembly is the same
between the old and new versions:

```
mov eax, edi
add dl, -1
sbb eax, esi
setb dl
ret
```

Author: pietroalbini

library/core/src/num/uint_macros.rs

@@ -1606,7 +1606,7 @@ macro_rules! uint_impl {
             //   to generate optimal code for now, and LLVM doesn't have an equivalent intrinsic
             let (a, b) = self.overflowing_sub(rhs);
             let (c, d) = a.overflowing_sub(borrow as $SelfT);
-            (c, b | d)
+            (c, b || d)
         }
 
         /// Computes the absolute difference between `self` and `other`.