Remove links to feature gated functions

The `crate::encode`, `crate::decode`, and `Hrp::to_lowercase` functions
are feature gated on "alloc" so these links break builds that do not
enable the feature. Just use code ticks instead.

src/lib.rs

@@ -13,7 +13,7 @@
 //!
 //! - If you are doing segwit stuff you likely want to use the [`segwit`] API.
 //! - Non-segwit stuff and you have an allocator, use the top level API. For normal usage the
-//!   [`encode`] and [`decode`] functions should suffice. There are also various other functions for
+//!   `encode` and `decode` functions should suffice. There are also various other functions for
 //!   explicit control of the checksum algorithm and the case used when encoding.
 //! - Non-segwit stuff and you do *not* have an allocator, use the [`CheckedHrpstring`] type for
 //!   decoding. For encoding we provide various top level functions of the form `encode*_to_fmt`.

src/primitives/hrp.rs

@@ -221,7 +221,7 @@ impl Hrp {
 /// Displays the human-readable part.
 ///
 /// If an uppercase HRP was parsed during object construction then the returned string will be
-/// in uppercase also. For a lowercase string see [`Self::to_lowercase`].
+/// in uppercase also. For a lowercase string see `Self::to_lowercase`.
 impl fmt::Display for Hrp {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         for c in self.char_iter() {