syntax: remove WordBoundary::is_negated method

This is apparently not used anywhere. So drop it.

Also motivated by wanting to squash look-around assertions into a single
enum. So 'is_negated' won't make sense on its own anymore.

Author: BurntSushi

regex-syntax/src/hir/mod.rs

@@ -1353,16 +1353,6 @@ pub enum WordBoundary {
     AsciiNegate,
 }
 
-impl WordBoundary {
-    /// Returns true if and only if this word boundary assertion is negated.
-    pub fn is_negated(&self) -> bool {
-        match *self {
-            WordBoundary::Unicode | WordBoundary::Ascii => false,
-            WordBoundary::UnicodeNegate | WordBoundary::AsciiNegate => true,
-        }
-    }
-}
-
 /// The high-level intermediate representation for a group.
 ///
 /// This represents one of three possible group types: