int_log10.rs: change top level doc comments to outer

Author: hkBst

library/core/src/num/int_log10.rs

@@ -1,5 +1,5 @@
-/// These functions compute the integer logarithm of their type, assuming
-/// that someone has already checked that the value is strictly positive.
+//! These functions compute the integer logarithm of their type, assuming
+//! that someone has already checked that the value is strictly positive.
 
 // 0 < val <= u8::MAX
 #[inline]