[test] Fix js-perf config

The android_arm config is deprecated. We only use the v8 arch
strings.

NOTRY=true
TBR=adamk, caitp

Review-Url: https://codereview.chromium.org/2412513002
Cr-Commit-Position: refs/heads/master@{#40172}

test/js-perf-test/JSTests.json

 {
   "name": "JSTests",
   "run_count": 3,
-  "run_count_android_arm": 1,
-  "run_count_android_arm64": 1,
+  "run_count_arm": 1,
+  "run_count_arm64": 1,
   "timeout": 120,
   "units": "score",
   "total": true,
@@ -119,7 +119,7 @@
       "results_regexp": "^%s\\-Strings\\(Score\\): (.+)$",
       "run_count": 1,
       "timeout": 240,
-      "timeout_android_arm": 360,
+      "timeout_arm": 360,
       "tests": [
         {"name": "StringFunctions"}
       ]