Reword the docstring in todo! macro definition

Author: kormosi

library/core/src/macros/mod.rs

@@ -712,8 +712,8 @@ macro_rules! unimplemented {
 
 /// Indicates unfinished code.
 ///
-/// This can be useful if you are prototyping and are just looking to have your
-/// code typechecked.
+/// This can be useful if you are prototyping and just
+/// want a placeholder to let your code pass type analysis.
 ///
 /// The difference between [`unimplemented!`] and `todo!` is that while `todo!` conveys
 /// an intent of implementing the functionality later and the message is "not yet