[LyX features/biginset] Improve const correctness.

[Thibaut Cuvelier]

commit b1a4eb118cd3d271a35b2260cde077e21c62c32c
Author: Thibaut Cuvelier <tcuvelier at lyx.org>
Date:   Mon Mar 11 01:15:48 2024 +0100

    Improve const correctness.
---
 src/mathed/MathExtern.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/mathed/MathExtern.cpp b/src/mathed/MathExtern.cpp
index d101904e83..b07c08b56e 100644
--- a/src/mathed/MathExtern.cpp
+++ b/src/mathed/MathExtern.cpp
@@ -295,7 +295,7 @@ bool testString(MathAtom const & at, char const * const str)
 // search end of nested sequence
 MathData::iterator endNestSearch(
 	MathData::iterator it,
-	MathData::iterator last,
+	const MathData::iterator& last,
 	TestItemFunc testOpen,
 	TestItemFunc testClose
 )