Fix all dead-code warnings in cranelift-codegen-meta

cranelift/codegen/meta/src/cdsl/settings.rs

@@ -150,14 +150,6 @@ impl SettingGroup {
         }
         panic!("Should have found bool setting by name.");
     }
-
-    pub fn predicate_by_name(&self, name: &'static str) -> SettingPredicateNumber {
-        self.predicates
-            .iter()
-            .find(|pred| pred.name == name)
-            .unwrap_or_else(|| panic!("unknown predicate {}", name))
-            .number
-    }
 }
 
 /// This is the basic information needed to track the specific parts of a setting when building