ml-model-public: Fix upstream iree breakage

renaming mhlo to mhlo-legacy due to
https://github.com/openxla/iree/pull/13870.

Will further renaming to stablehlo once mnist.mlir is updated.

Change-Id: I077a21979da4712f1c04f93072f1ae541cd319c2

float_models/CMakeLists.txt

diff --git a/float_models/CMakeLists.txt b/float_models/CMakeLists.txt
index 6c57aa1..9bf848a 100644
--- a/float_models/CMakeLists.txt
+++ b/float_models/CMakeLists.txt
@@ -29,7 +29,7 @@
   C_IDENTIFIER
     "float_models_mnist"
   FLAGS
-    "-iree-input-type=mhlo"
+    "-iree-input-type=mhlo_legacy"
   RVV_OFF
 )