df: migrate OptionsError to thiserror

Closes #7536

Author: lewisboon

src/uu/df/src/df.rs

@@ -126,7 +126,10 @@ enum OptionsError {
     #[error("option --output: field {0} used more than once")]
     ColumnError(ColumnError),
 
-    #[error("{}", .0.iter().map(|t| format!("file system type {} both selected and excluded", t.quote())).collect::<Vec<String>>().join(format!("\n{}: ", uucore::util_name()).as_str()))]
+    #[error("{}", .0.iter()
+            .map(|t| format!("file system type {} both selected and excluded", t.quote()))
+            .collect::<Vec<_>>()
+            .join(format!("\n{}: ", uucore::util_name()).as_str()))]
     FilesystemTypeBothSelectedAndExcluded(Vec<String>),
 }