nostr: fix missing FromStr import

Author: OverOrion

crates/nostr/src/types/channel_id.rs

@@ -9,6 +9,9 @@ use alloc::{
     vec::Vec,
 };
 
+#[cfg(all(feature = "alloc", not(feature = "std")))]
+use core::str::FromStr;
+
 #[cfg(all(feature = "alloc", not(feature = "std")))]
 use alloc::fmt;
 #[cfg(feature = "std")]