[js-perf-test] Fix JSON syntax for RegExp tests

test/js-perf-test/RegExp/RegExpTests.json

 {
   "name": "RegExpTests",
   "run_count": 5,
   "run_count_android_arm": 3,
   "run_count_android_arm64": 3,
   "timeout": 120,
   "units": "score",
   "total": true,
   "resources": ["base.js"],
   "tests": [
@@ skipping 18 matching lines @@
         "replace.js",
         "search.js",
         "split.js",
         "test.js",
         "slow_exec.js",
         "slow_flags.js",
         "slow_match.js",
         "slow_replace.js",
         "slow_search.js",
         "slow_split.js",
-        "slow_test.js",
+        "slow_test.js"
       ],
       "results_regexp": "^%s\\-RegExp\\(Score\\): (.+)$",
       "tests": [
         {"name": "Ctor"},
         {"name": "Exec"},
         {"name": "Flags"},
         {"name": "Match"},
         {"name": "Replace"},
         {"name": "Search"},
         {"name": "Split"},
         {"name": "Test"},
         {"name": "SlowExec"},
         {"name": "SlowFlags"},
         {"name": "SlowMatch"},
         {"name": "SlowReplace"},
         {"name": "SlowSearch"},
         {"name": "SlowSplit"},
-        {"name": "SlowTest"},
+        {"name": "SlowTest"}
       ]
     }
   ]
 }