[range.slide.overview] Fix bad quotation marks for string-literal (#5326)

Author: hewillk

source/ranges.tex

@@ -11923,7 +11923,7 @@
 vector v = {1, 2, 3, 4};
 
 for (auto i : v | views::slide(2)) {
-  cout << '[' << i[0] << ', ' << i[1] << "] ";          // prints: [1, 2] [2, 3] [3, 4]
+  cout << '[' << i[0] << ", " << i[1] << "] ";          // prints: [1, 2] [2, 3] [3, 4]
 }
 \end{codeblock}
 \end{example}