Remove param doxygen comment for non-existing parameter.

Found by -Wdocumentation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199814 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/Disassembler/X86Disassembler.cpp

@@ -236,7 +236,6 @@ static const uint8_t segmentRegnums[SEG_OVERRIDE_max] = {
 /// translateSrcIndex   - Appends a source index operand to an MCInst.
 ///
 /// @param mcInst       - The MCInst to append to.
-/// @param operand      - The operand, as stored in the descriptor table.
 /// @param insn         - The internal instruction.
 static bool translateSrcIndex(MCInst &mcInst, InternalInstruction &insn) {
   unsigned baseRegNo;