[CINN] Remove legacy FusionIters code (#71890)

Author: huangjiyi

paddle/cinn/operator_fusion/pir_graph_analyzing/CMakeLists.txt

@@ -1,8 +1,2 @@
-gather_srcs(
-  fusion_graph_analyzing
-  SRCS
-  shardable_axes_base.cc
-  dim_relation.cc
-  fusion_iters.cc
-  loop_axis_mapping.cc
-  loop_transform_analysis.cc)
+gather_srcs(fusion_graph_analyzing SRCS shardable_axes_base.cc dim_relation.cc
+            loop_axis_mapping.cc loop_transform_analysis.cc)