Merge rust-bitcoin#5064: fix: FromStd::inner_mut deprecation note

b5e1edd fix: FromStd::inner_mut deprecation note (VolodymyrBg)

Pull request description:

  Update the deprecation note on FromStd::inner_mut() to recommend get_mut() instead of get_ref(). This aligns with the intended API where inner() maps to get_ref() and the mutable variant maps to get_mut().


ACKs for top commit:
  apoelstra:
    ACK b5e1edd; successfully ran local tests; nice find


Tree-SHA512: fa1ab3f28de8513893c0c68fc5e394413221e9aab5de4015308df125f62e1e7c2ee76a2d4c6fcca00aef05dd6bc4d774589af9fc6fdff5c32c52fc342e0318bb

Author: apoelstra

io/src/bridge.rs

@@ -40,7 +40,7 @@ impl<T> FromStd<T> {
 
     /// Returns a mutable reference to the wrapped value.
     #[inline]
-    #[deprecated(since = "TBD", note = "use `get_ref()` instead")]
+    #[deprecated(since = "TBD", note = "use `get_mut()` instead")]
     pub fn inner_mut(&mut self) -> &mut T { &mut self.0 }
 }