[rust][LSC] Prepare for toolchain roll

Remove uses of deprecated std::error::Error::description.

Change-Id: I7f980e8e4d411e818ef468aefd50d94228d80397
diff --git a/src/connectivity/network/http_client/src/main.rs b/src/connectivity/network/http_client/src/main.rs
index a02731c..ac3e68d 100644
--- a/src/connectivity/network/http_client/src/main.rs
+++ b/src/connectivity/network/http_client/src/main.rs
@@ -12,7 +12,6 @@
 use futures::compat::Future01CompatExt;
 use futures::prelude::*;
 use hyper;
-use std::error::Error as stderr;
 
 fn version_to_str(version: hyper::Version) -> &'static str {
     match version {
@@ -106,7 +105,7 @@
         url: None,
         error: Some(Box::new(oldhttp::HttpError {
             code: to_error_code(&error),
-            description: Some(error.description().to_string()),
+            description: Some(error.to_string()),
         })),
         status_line: None,
         headers: None,
diff --git a/tools/fidl/fidldoc/src/fidljson.rs b/tools/fidl/fidldoc/src/fidljson.rs
index 9d9b7de..87435e4 100644
--- a/tools/fidl/fidldoc/src/fidljson.rs
+++ b/tools/fidl/fidldoc/src/fidljson.rs
@@ -8,7 +8,6 @@
 use serde_json::Value;
 
 use std::collections::HashMap;
-use std::error::Error;
 use std::fs::File;
 use std::io;
 use std::io::prelude::*;
@@ -48,7 +47,7 @@
                 eprintln!(
                     "Couldn't open file {path}: {reason}",
                     path = path.display(),
-                    reason = why.description()
+                    reason = why,
                 );
                 return Err(why);
             }