Fix typo in iOS64 Perf configuration.

TBR=phoglund@webrtc.org

Bug: webrtc:7156
No-Try: true
Change-Id: I34fb403a4462af07f76d64db64f85207060163ab
Reviewed-on: https://webrtc-review.googlesource.com/20503
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Reviewed-by: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20575}

tools_webrtc/ios/internal.client.webrtc/iOS64_Perf.json

@@ -16,7 +16,7 @@
   },
   "use_analyze": false,
   "additional_compile_targets": [ "all" ],
-  "configuration": "Debug",
+  "configuration": "Release",
   "bucket": "chromium-webrtc",
   "tests": [
     {