Change iOS Simulator bot to 32-bit and iPhone 5.

Before promoting it to the main waterfall I thought it made
sense to ensure it works for a phone that actually is 32-bit
(iPhone 6s isn't). It also makes more sense to run the older
iOS version (9) on the older phone.

BUG=chromium:677385
TBR=ehmaldonado@webrtc.org

Review-Url: https://codereview.webrtc.org/2604203002 .
Cr-Commit-Position: refs/heads/master@{#15837}

tools-webrtc/mb/mb_config.pyl

@@ -88,7 +88,7 @@
     'client.webrtc.fyi': {
       # Mac
       'Mac (swarming)': 'release_bot_x64',
-      'iOS64 Sim Debug (iOS 9.0)': 'ios_debug_static_bot_x64',
+      'iOS32 Sim Debug (iOS 9.0)': 'ios_debug_static_bot_x86',
 
       # Linux
       'Linux64 GCC': 'gcc_release_bot_x64',

webrtc/build/ios/client.webrtc.fyi/iOS32_Sim_Debug_(iOS_9.0).json

@@ -3,7 +3,7 @@
     "kjellander"
   ],
   "comments": [
-    "Tests for 64-bit iOS simulators.",
+    "Tests for 32-bit iOS simulators.",
     "gn_args in this file is only read by the buildbot recipe; ",
     "webrtc/build/mb_config.pyl contains the actual build configuration.",
     "TODO(kjellander): remove gn_args when the recipe is updated."
@@ -19,7 +19,7 @@
   "tests": [
     {
       "include": "common_tests.json",
-      "device type": "iPhone 6s",
+      "device type": "iPhone 5",
       "os": "9.0"
     }
   ]