Reduce thread count for 719-varhandle-concurrency test

This includes the revert of the temporary measure for the failing
test (Ie4f11f53b8b3fb1507bf7dc0a2dae018f48aa573).

Fixes: 229958698
Test: Reverted arm32 register clobbering fix and see test still
      catches the error
      (see I14d51f0aa1e26de82be7077ac5597bbeec476dcd)
Change-Id: I49a399826cc09863f2ea3ebdf40acf5845892f7f
diff --git a/test/719-varhandle-concurrency/src/Main.java b/test/719-varhandle-concurrency/src/Main.java
index 1c2135b..f89a0bb 100644
--- a/test/719-varhandle-concurrency/src/Main.java
+++ b/test/719-varhandle-concurrency/src/Main.java
@@ -39,7 +39,7 @@
   }
 
   private static final int TASK_COUNT = 10000;
-  private static final int THREAD_COUNT = 100;
+  private static final int THREAD_COUNT = 20;
   /* Each test may need several retries before a concurrent failure is seen. In the past, for a
    * known bug, between 5 and 10 retries were sufficient. Use RETRIES to configure how many
    * iterations to retry for each test scenario. However, to avoid the test running for too long,
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 8b18d17..c258f0f 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -1498,10 +1498,5 @@
         "variant": "target & ndebug & 64",
         "bug": "b/224733324",
         "description": ["segfault in VarHandle::GetMethodTypeMatchForAccessMode"]
-    },
-    {
-        "tests": ["719-varhandle-concurrency"],
-        "bug": "b/229958698",
-        "description": ["SIGSEGV in pthread_create"]
     }
 ]