Fix libyuv version comment in reformat_libyuv.c
diff --git a/src/reformat_libyuv.c b/src/reformat_libyuv.c
index ab96bec..e8d6af8 100644
--- a/src/reformat_libyuv.c
+++ b/src/reformat_libyuv.c
@@ -63,7 +63,7 @@
// These defines are used to create a NULL reference to libyuv functions that
// did not exist prior to a particular version of libyuv.
-// Versions prior to 1750 are considered too old and not checked.
+// Versions prior to 1755 are considered too old and not used (see CMakeLists.txt).
#if LIBYUV_VERSION < 1840
#define ABGRToJ400 NULL
#endif
