docs: stop labelling current behaviour as legacy

Three of the five comments the audit found. always() accepts a predicate or a
formula and both are live: the shipped default properties pass a predicate, the
six example-spec properties pass a formula. String selectors are documented
first-class beside object selectors in spec-language.md. "all" is the
--platform flag's default value, not an older calling convention.

internal/driver/chrome/translate.go

@@ -13,7 +13,7 @@ import (
 // `foo]:has(*),body[x="..."]` that would escape the intended match.
 var attrNamePattern = regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9_-]*$`)
 
-// TranslateStringSelector converts a legacy string selector ("id:foo",
+// TranslateStringSelector converts a string selector ("id:foo",
 // "descPrefix:bar") into a CSS selector or XPath expression usable from the
 // chrome driver's TapSelector fallback path. The boolean return is true when
 // the result is XPath rather than CSS. Unknown prefixes pass through to a CSS