Adjust known test failures after recent changes in ART test configurations.

Changes:
- Have test 641-checker-arraycopy always run.
- Have test 537-checker-arraycopy always run, except the table-lookup
  read barrier configuration.

Test: Run ART run-tests with ART_READ_BARRIER_TYPE=TABLELOOKUP
Test: Run ART run-tests without ART_READ_BARRIER_TYPE=TABLELOOKUP
Bug: 62611253
Change-Id: Ib4b1e96c85b42cb6acb854229acd1df83d04cf5f
diff --git a/test/knownfailures.json b/test/knownfailures.json
index d1855dc..44805ad 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -344,10 +344,8 @@
         "variant": "optimizing | regalloc_gc"
     },
     {
-        "tests": ["537-checker-arraycopy",
-                  "641-checker-arraycopy"],
-        "env_vars": {"ART_USE_READ_BARRIER": "true"},
-        "variant": "interpreter | optimizing | regalloc_gc | jit"
+        "tests": ["537-checker-arraycopy"],
+        "env_vars": {"ART_READ_BARRIER_TYPE": "TABLELOOKUP"}
     },
     {
         "tests": ["476-clinit-inline-static-invoke",