ART: Remove experimental flags for plugins and agents

Remove experimental flags guarding plugins and agents.

Partial revert of commit 7233c7e752c0d26387d143ee74420e9cd1f09390.
Partial revert of commit 185d134a3b43ab7529053e965917e0fa74bceba4.

Bug: 31455788
Test: m test-art-host
Change-Id: I11a19f24b88ced8da7a28e2cb7a2f602aab884a8
diff --git a/test/915-obsolete-2/run b/test/915-obsolete-2/run
index 4379349..c6e62ae 100755
--- a/test/915-obsolete-2/run
+++ b/test/915-obsolete-2/run
@@ -14,6 +14,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-./default-run "$@" --experimental agents \
-                   --experimental runtime-plugins \
-                   --jvmti
+./default-run "$@" --jvmti