[string.view.access] Use const charT* for data

for consistency with `basic_string`

Author: frederick-vs-ja

source/strings.tex

@@ -1110,7 +1110,7 @@
 
 \indexlibrarymember{data}{basic_string_view}%
 \begin{itemdecl}
-constexpr const_pointer data() const noexcept;
+constexpr const charT* data() const noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}