descriptor: drop to_string_no_chksum method

This method has been made redundant by the `{:#}` display specifier
since 7577e8c two years ago. It is
poorly named, inefficient since it always requires allocating a
`String`, and also broken because it uses debug display for keys.

All of our unit tests were converted over to use :# which is why it
wasn't noticed that this method didn't work.

Fixes #34
Fixes #85

Author: apoelstra

CHANGELOG.md

@@ -1,3 +1,7 @@
+# Unreleased
+
+- [Removed `to_string_no_chksum`](https://github.com/ElementsProject/elements-miniscript/pull/86). This method was poorly-named and broken. Use the alternate display `{:#}` formatter instead to format descriptors without a checksum.
+
 # 0.3.1 - May 10, 2024
 
 - [Fixed](https://github.com/ElementsProject/elements-miniscript/pull/81) ELIP-151 hash calculation

src/descriptor/csfs_cov/mod.rs

@@ -84,7 +84,7 @@ mod tests {
 
     fn string_rtt(desc_str: &str) {
         let desc = Descriptor::<String>::from_str(desc_str).unwrap();
-        assert_eq!(desc.to_string_no_chksum(), desc_str);
+        assert_eq!(format!("{:#}", desc), desc_str);
         let cov_desc = desc.as_cov().unwrap();
         assert_eq!(cov_desc.to_string(), desc.to_string());
     }

src/descriptor/mod.rs

@@ -434,10 +434,6 @@ impl<Pk: MiniscriptKey, Ext: Extension> Descriptor<Pk, Ext> {
         }
     }
 
-    /// Return a string without the checksum
-    pub fn to_string_no_chksum(&self) -> String {
-        format!("{:?}", self)
-    }
     /// Checks whether the descriptor is safe.
     ///
     /// Checks whether all the spend paths in the descriptor are possible on the