[cxx-interop] Fix typo unkwon -> unknown

Author: cabmeurer

test/SILOptimizer/array_element_propagation_ossa_nontrivial.sil

@@ -204,7 +204,7 @@ bb0(%arg0 : @owned $MyKlass, %arg1 : @owned $MyKlass, %arg2 : @owned $MyKlass):
   return %52 : $()
 }
 
-sil [ossa] @unkown_use : $@convention(thin) (@owned MyKlass) -> () {
+sil [ossa] @unknown_use : $@convention(thin) (@owned MyKlass) -> () {
 bb0(%arg0 : @owned $MyKlass):
   %0 = function_ref @swift_bufferAllocate : $@convention(thin) () -> @owned _ContiguousArrayStorage<MyKlass>
   %1 = integer_literal $Builtin.Word, 1

utils/build_swift/tests/build_swift/test_driver_arguments.py

@@ -278,7 +278,7 @@ def test(self):
                 [option.option_string])
             # The argument should never show up in the namespace
             self.assertFalse(hasattr(namespace, option.dest))
-            # It should instead be forwareded to unkown_args
+            # It should instead be forwareded to unknown_args
             self.assertEqual(unknown_args, [option.option_string])
 
         return test