Make ChainEndpoint::get_key take &self instead of &mut self (#3732

)

Updates the `get_key` method on the `ChainEndpoint` trait to take `&self` instead of `&mut self`, as it wasn't needed for self to be mutable. it's also expected that a function named as `get` doesn't mutate self. this also allows `get_key` to be used in methods that take `&self`.

crates/relayer/src/chain/cosmos.rs

@@ -941,7 +941,7 @@ impl ChainEndpoint for CosmosSdkChain {
         &mut self.keybase
     }
 
-    fn get_key(&mut self) -> Result<Self::SigningKeyPair, Error> {
+    fn get_key(&self) -> Result<Self::SigningKeyPair, Error> {
         // Get the key from key seed file
         let key_pair = self
             .keybase()

crates/relayer/src/chain/endpoint.rs

@@ -112,7 +112,7 @@ pub trait ChainEndpoint: Sized {
     fn get_signer(&self) -> Result<Signer, Error>;
 
     /// Get the signing key pair
-    fn get_key(&mut self) -> Result<Self::SigningKeyPair, Error>;
+    fn get_key(&self) -> Result<Self::SigningKeyPair, Error>;
 
     fn add_key(&mut self, key_name: &str, key_pair: Self::SigningKeyPair) -> Result<(), Error> {
         self.keybase_mut()