halide2isl.h: drop references to ReductionInit markers

findReductions stopped looking at them in 33a3bb6 (halide2isl: do not
require init statement for reduction detection,
Sun May 27 12:04:46 2018 +0200) and they have been removed completely
in d67e305 (tc2halide: refrain from marking reduction init nodes,
Tue May 29 11:58:42 2018 +0200).

Author: Sven Verdoolaege

tc/core/halide2isl.h

@@ -93,7 +93,7 @@ ScheduleTreeAndAccesses makeScheduleTree(
     const Halide::Internal::Stmt& s);
 
 /// Enumerate all reductions in a statement, by looking for the
-/// ReductionInit and ReductionUpdate markers inserted during lowering
+/// ReductionUpdate markers inserted during lowering
 /// (see tc2halide.h).
 /// Each reduction object stores a reference to
 /// the update statement, and a list of reduction dimensions