Revert "Making CompletableFutureTest as known failure on gcstress debug"

This reverts changes I5845b79dd85dae3ce3ab5914761fc54b8f1da4f0
and I4f06af6ad38ea6ecb39cbb160ef5862cf3d12f87.

The fix in I0846ed1aebe93e4a3fbb9c7189f73bd7f86357e6 that adds a
delay factor for gcstress tests is enough to allow enough time
for the test to complete.

Fixes: 205007075
Test: art/tools/run-libcore-tests.sh --mode host --gcstress \
      --variant X32 --debug jsr166.CompletableFutureTest
      # ran with and without the delay factor for gcstress
Change-Id: I68d342d26004d85f7ae546c9eeb1034f6f9e430b

tools/libcore_gcstress_debug_failures.txt

diff --git a/tools/libcore_gcstress_debug_failures.txt b/tools/libcore_gcstress_debug_failures.txt
index 2193189..de68b61 100644
--- a/tools/libcore_gcstress_debug_failures.txt
+++ b/tools/libcore_gcstress_debug_failures.txt
@@ -63,13 +63,5 @@
   names: ["libcore.java.lang.ThreadTest#nativeThreadNames",
           "jsr166.ThreadLocalTest#testGenericITL"
   ]
-},
-{
-  description: "Time-sensitive test fails check of elapsed time with gcstress",
-  result: EXEC_FAILED,
-  bug: 205007075,
-  names: ["jsr166.CompletableFutureTest#testCompleteOnTimeout_completed",
-          "jsr166.CompletableFutureTest#testDelayedExecutor"
-         ]
 }
 ]