expr: Remove incorrect comment

Author: frendsick

src/uu/expr/src/syntax_tree.rs

@@ -166,7 +166,6 @@ impl StringOp {
                 };
 
                 // Handle the rest of the input pattern.
-                // Escaped previous character should not affect the current.
                 let mut prev = first.unwrap_or_default();
                 let mut prev_is_escaped = false;
                 while let Some(curr) = pattern_chars.next() {