8260584: Shenandoah: simplify "Concurrent Thread Roots" logging

Reviewed-by: rkennke, zgu

Author: shipilev

src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp

@@ -73,9 +73,8 @@ class outputStream;
   f(init_evac,                                      "  Initial Evacuation")            \
   SHENANDOAH_PAR_PHASE_DO(evac_,                    "    E: ", f)                      \
                                                                                        \
-  f(conc_thread_roots,                              "Concurrent Stack Processing")     \
-  f(conc_thread_roots_work,                           "  Threads")                     \
-  SHENANDOAH_PAR_PHASE_DO(conc_thread_roots_work_,    "    CT: ", f)                   \
+  f(conc_thread_roots,                              "Concurrent Thread Roots")         \
+  SHENANDOAH_PAR_PHASE_DO(conc_thread_roots_,       "  CTR: ", f)                      \
   f(conc_weak_refs,                                 "Concurrent Weak References")      \
   f(conc_weak_refs_work,                            "  Process")                       \
   SHENANDOAH_PAR_PHASE_DO(conc_weak_refs_work_,     "    CWRF: ", f)                   \