sdk: get rid of the UnableToCloneRequest error which is absolutely unused

crates/matrix-sdk/CHANGELOG.md

@@ -15,6 +15,8 @@ Breaking changes:
 - It is now possible to select the format of a generated thumbnail.
   - `generate_image_thumbnail` takes a `ThumbnailFormat`.
   - `AttachmentConfig::generate_thumbnail` takes a `ThumbnailFormat`.
+- The `HttpError::UnableToCloneRequest` error variant has been removed because it was never used or
+  generated by the SDK.
 
 Additions:
 

crates/matrix-sdk/src/error.rs

@@ -105,10 +105,6 @@ pub enum HttpError {
     #[error(transparent)]
     IntoHttp(#[from] IntoHttpError),
 
-    /// The given request can't be cloned and thus can't be retried.
-    #[error("The request cannot be cloned")]
-    UnableToCloneRequest,
-
     /// An error occurred while refreshing the access token.
     #[error(transparent)]
     RefreshToken(#[from] RefreshTokenError),