Address @ilogiq's nits

tests/compile-fail/methods.rs

@@ -373,6 +373,9 @@ fn single_char_pattern() {
     // Not yet testing for multi-byte characters
     // Changing `r.len() == 1` to `r.chars().count() == 1` in `lint_single_char_pattern`
     // should have done this but produced an ICE
+    //
+    // We may not want to suggest changing these anyway
+    // See: https://github.com/Manishearth/rust-clippy/issues/650#issuecomment-184328984
     x.split("ß");
     x.split("ℝ");
     x.split("💣");