Simplify the collector names.

To make it easier to distinguish the collector names in the GC logs.

Bug: 12687968
Test: test-art-host with CC.
Change-Id: I23d06a4f8f4b0447d0904c0cb813e080277a2e9e
diff --git a/runtime/gc/collector/concurrent_copying.cc b/runtime/gc/collector/concurrent_copying.cc
index dccec9f..ccb3d6d 100644
--- a/runtime/gc/collector/concurrent_copying.cc
+++ b/runtime/gc/collector/concurrent_copying.cc
@@ -58,7 +58,7 @@
                                      bool measure_read_barrier_slow_path)
     : GarbageCollector(heap,
                        name_prefix + (name_prefix.empty() ? "" : " ") +
-                       "concurrent copying + mark sweep"),
+                       "concurrent copying"),
       region_space_(nullptr), gc_barrier_(new Barrier(0)),
       gc_mark_stack_(accounting::ObjectStack::Create("concurrent copying gc mark stack",
                                                      kDefaultGcMarkStackSize,