[docs] Apply previous sphinx fix to its actual source

This clang-format documentation file is auto-generated from Format.h,
so the fix should be applied there, or else it will be overwritten
whenever Format.h is modified and that file is regenerated.

Author: rymiel

clang/include/clang/Format/Format.h

@@ -2501,7 +2501,7 @@ struct FormatStyle {
   /// \endcode
   struct IntegerLiteralSeparatorStyle {
     /// Format separators in binary literals.
-    /// \code
+    /// \code{.text}
     ///    -1: 0b100111101101
     ///     0: 0b10011'11'0110'1
     ///     3: 0b100'111'101'101