Update outdated documentation referencing clear_refs.

Change-Id: Ifcac1f7c08bc47bb017ed477d3d7e8a31bf3669a
diff --git a/tools/heap_profile b/tools/heap_profile
index acf9d73..5d76a4e 100755
--- a/tools/heap_profile
+++ b/tools/heap_profile
@@ -151,7 +151,7 @@
                       "this can significantly slow down the client.",
                       action="store_true")
   parser.add_argument("--idle-allocations", help="Keep track of how many "
-                      "bytes were unused since the last clear_refs, per "
+                      "bytes were unused since the last dump, per "
                       "callstack", action="store_true")
   parser.add_argument("--simpleperf", action="store_true",
                       help="Get simpleperf profile of heapprofd. This is "