Revert "Reduce libcore parallelism for host"

This reverts commit 9d00bf1e0a9441153e69ea26c4cf111690a6e6a8.

Reason for revert: It didn't help. I hope the timeout increase helps instead.

Change-Id: I53aaf33a2e9db35bbc25acf89d08fc471e8f60e5
diff --git a/tools/run-libcore-tests.py b/tools/run-libcore-tests.py
index ba3c090..3ebee09 100755
--- a/tools/run-libcore-tests.py
+++ b/tools/run-libcore-tests.py
@@ -218,13 +218,7 @@
       raise AssertionError(f"Missing {jar}. Run buildbot-build.sh first.")
 
   if not args.jobs:
-    if args.mode == "device":
-      args.jobs = get_target_cpu_count()
-    else:
-      args.jobs = multiprocessing.cpu_count()
-      if args.gcstress:
-        # TODO: Investigate and fix the underlying issues.
-        args.jobs = args.jobs // 2
+    args.jobs = get_target_cpu_count() if args.mode == "device" else multiprocessing.cpu_count()
 
   def run_test(test_name):
     cmd = " ".join(get_vogar_command(test_name))