[RISCV][NFC] Fix typo in RISCVIndirectBranchTracking.cpp (#157221)

Author: jaidTw

llvm/lib/Target/RISCV/RISCVIndirectBranchTracking.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// The pass adds LPAD (AUIPC with rs1 = X0) machine instructions at the
+// The pass adds LPAD (AUIPC with rd = X0) machine instructions at the
 // beginning of each basic block or function that is referenced by an indirect
 // jump/call instruction.
 //