Remove this fixme, looking at the linker source, all targets pad to 4 bytes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93835 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCAssembler.cpp

@@ -679,8 +679,6 @@ public:
       UndefinedSymbolData[i].SymbolData->setIndex(Index++);
 
     // The string table is padded to a multiple of 4.
-    //
-    // FIXME: Check to see if this varies per arch.
     while (StringTable.size() % 4)
       StringTable += '\x00';
   }