fix a couple clippy:complexitys

double_parens
 filter_map_identity
 needless_question_mark
 redundant_guards

compiler/rustc_middle/src/mir/pretty.rs

@@ -277,9 +277,9 @@ pub fn create_dump_file<'tcx>(
             )
         })?;
     }
-    Ok(fs::File::create_buffered(&file_path).map_err(|e| {
+    fs::File::create_buffered(&file_path).map_err(|e| {
         io::Error::new(e.kind(), format!("IO error creating MIR dump file: {file_path:?}; {e}"))
-    })?)
+    })
 }
 
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