[GlobalISel] Remove an unnecessary cast (NFC) (#146249)

Idx is already of unsigned.

llvm/lib/CodeGen/GlobalISel/LoadStoreOpt.cpp

diff --git a/llvm/lib/CodeGen/GlobalISel/LoadStoreOpt.cpp b/llvm/lib/CodeGen/GlobalISel/LoadStoreOpt.cpp
index 1c41501..b2f8435 100644
--- a/llvm/lib/CodeGen/GlobalISel/LoadStoreOpt.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LoadStoreOpt.cpp
@@ -458,7 +458,7 @@
     for (auto AliasInfo : reverse(C.PotentialAliases)) {
       MachineInstr *PotentialAliasOp = AliasInfo.first;
       unsigned PreCheckedIdx = AliasInfo.second;
-      if (static_cast<unsigned>(Idx) < PreCheckedIdx) {
+      if (Idx < PreCheckedIdx) {
         // Once our store index is lower than the index associated with the
         // potential alias, we know that we've already checked for this alias
         // and all of the earlier potential aliases too.