[LyX/master] Fixup ce526607 again: last-minute blunder

[Jean-Marc Lasgouttes]

commit acce7a9ce87f9d5ebfd05a4d788e97991597a1a7
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Tue Nov 3 16:22:20 2020 +0100

    Fixup ce526607 again: last-minute blunder
---
 config/lyxinclude.m4 |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index b1027fe..fb6525c 100644
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -311,7 +311,7 @@ AC_REQUIRE([AC_PROG_CXXCPP])
 ### We might want to force the C++ standard.
 AC_ARG_ENABLE(cxx-mode,
   AS_HELP_STRING([--enable-cxx-mode],[choose C++ standard (default: 14, then 11)]),,
-  [enable_cxx_mode="14,11"]
+  [enable_cxx_mode={14,11}]
 )
 
 AC_LANG_PUSH(C++)