refactor(docs): Use intra-doc links to avoid breakages

Author: epage

src/builder/arg.rs

@@ -466,7 +466,6 @@ impl Arg {
     /// [`Arg::short`]: Arg::short()
     /// [`Arg::long`]: Arg::long()
     /// [`Arg::num_args(true)`]: Arg::num_args()
-    /// [`panic!`]: https://doc.rust-lang.org/std/macro.panic!.html
     /// [`Command`]: crate::Command
     #[inline]
     #[must_use]

src/macros.rs

@@ -533,7 +533,7 @@ macro_rules! arg_impl {
 /// assert_eq!(*m.get_one::<u8>("debug").unwrap(), 0);
 /// assert_eq!(m.get_one::<String>("input"), None);
 /// ```
-/// [`Arg`]: ./struct.Arg.html
+/// [`Arg`]: crate::Arg
 #[macro_export]
 macro_rules! arg {
     ( $name:ident: $($tail:tt)+ ) => {