[GlobalISel] Remove unused declaration tryCombineIndexedLoadStore

The corresponding function definition was removed by:

  commit 7e5c267
  Author: Amara Emerson <[email protected]>
  Date:   Mon Sep 25 03:22:25 2023 +0800

Author: kazutakahirata

llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h

@@ -194,9 +194,6 @@ class CombinerHelper {
   /// Match (and (load x), mask) -> zextload x
   bool matchCombineLoadWithAndMask(MachineInstr &MI, BuildFnTy &MatchInfo);
 
-  /// Combine \p MI into a pre-indexed or post-indexed load/store operation if
-  /// legal and the surrounding code makes it useful.
-  bool tryCombineIndexedLoadStore(MachineInstr &MI);
   bool matchCombineIndexedLoadStore(MachineInstr &MI, IndexedLoadStoreMatchInfo &MatchInfo);
   void applyCombineIndexedLoadStore(MachineInstr &MI, IndexedLoadStoreMatchInfo &MatchInfo);