[range.concat.overview] Remove unnecessary std:: prefix from example (#6931)

Author: hewillk

source/ranges.tex

@@ -8488,11 +8488,11 @@
 \end{itemize}
 \begin{example}
 \begin{codeblock}
-std::vector<int> v1{1, 2, 3}, v2{4, 5}, v3{};
-std::array a{6, 7, 8};
-auto s = std::views::single(9);
-for (auto&& i : std::views::concat(v1, v2, v3, a, s)) {
-  std::print("{} ", i);         // prints \tcode{1 2 3 4 5 6 7 8 9}
+vector<int> v1{1, 2, 3}, v2{4, 5}, v3{};
+array a{6, 7, 8};
+auto s = views::single(9);
+for (auto&& i : views::concat(v1, v2, v3, a, s)) {
+  print("{} ", i);      // prints \tcode{1 2 3 4 5 6 7 8 9}
 }
 \end{codeblock}
 \end{example}