Android: Update Android Studio canary version

- Submit this only when 3.4 is available on internal canary.

TBR=agrieve@chromium.org

Bug: 620034
Change-Id: Iebcec3271b37ecfea8ba4f3eac36ab576ec5acf1
Reviewed-on: https://chromium-review.googlesource.com/c/1324871Reviewed-by: Peter Wen <wnwen@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607220}

build/android/gradle/root.jinja

@@ -10,7 +10,7 @@ buildscript {
     }
     dependencies {
 {% if channel == 'canary' %}
-        classpath "com.android.tools.build:gradle:3.3.0-alpha13"
+        classpath "com.android.tools.build:gradle:3.4.0-alpha03"
 {% elif channel == 'beta' %}
         classpath "com.android.tools.build:gradle:3.1.0-beta4"
 {% else %}