Delete unused ParamPatternInfo::GetNameId (#4942)

Perhaps GetPrettyName replaced all uses?

As long as I'm here, also fix struct declaration order.

toolchain/check/pattern_match.cpp

@@ -18,7 +18,6 @@ namespace Carbon::Check {
 
 // Returns a best-effort name for the given ParamPattern, suitable for use in
 // IR pretty-printing.
-// TODO: Resolve overlap with SemIR::Function::ParamPatternInfo::GetNameId
 template <typename ParamPattern>
 static auto GetPrettyName(Context& context, ParamPattern param_pattern)
     -> SemIR::NameId {