[expr.ref] does not cover postfix-expression.template id-expression

[languagelawyer]

Full name of submitter (unless configured in github; will be published with the issue): Andrey Erokhin

Reference (section label): [expr.ref]

Link to reflector thread (if any): cplusplus/draft#4155

Issue description:

The first paragraph mentions optional template:

A postfix expression followed by a dot . or an arrow ->, optionally followed by the keyword template, and then followed by an id-expression, is a postfix expression.

but template is never mentioned in other paragraphs, and the rest of the subclause covers only postfix-expression.id-expression

Suggested resolution: