bdk_wallet: remove unnecessary calls to calc_checksum

This code was:
1. Removing the checksum from the descriptor string, asserting it was
   present
2. Re-calculating the checksum on the descriptor string absent the
   checksum

Instead, just use the existing checksum? If we don't trust it we
probably shouldn't assert its presence in the first place.

crates/wallet/src/wallet/mod.rs

@@ -79,7 +79,7 @@ use utils::{check_nsequence_rbf, After, Older, SecpCtx};
 
 use crate::descriptor::policy::BuildSatisfaction;
 use crate::descriptor::{
-    self, calc_checksum, DerivedDescriptor, DescriptorMeta, ExtendedDescriptor, ExtractPolicy,
+    self, DerivedDescriptor, DescriptorMeta, ExtendedDescriptor, ExtractPolicy,
     IntoWalletDescriptor, Policy, XKeyUtils,
 };
 use crate::psbt::PsbtUtils;
@@ -2360,15 +2360,13 @@ where
         .into_wallet_descriptor(secp, network)?
         .0
         .to_string();
-    let mut wallet_name = calc_checksum(&descriptor[..descriptor.find('#').unwrap()])?;
+    let mut wallet_name = descriptor.split_once('#').unwrap().1.to_string();
     if let Some(change_descriptor) = change_descriptor {
         let change_descriptor = change_descriptor
             .into_wallet_descriptor(secp, network)?
             .0
             .to_string();
-        wallet_name.push_str(
-            calc_checksum(&change_descriptor[..change_descriptor.find('#').unwrap()])?.as_str(),
-        );
+        wallet_name.push_str(change_descriptor.split_once('#').unwrap().1);
     }
 
     Ok(wallet_name)