android build: Allow Gradle to use more memory

Fixes zulip#1330.

Since Monday, CI builds have been running out of memory,
presumably due to some upstream change.  Allocate more memory
so that the CI can pass again.

The limit was 1.5 GiB, but now even 2.5 GiB doesn't seem to be
enough.  So increase it to 3 GiB.

CZO discussion:
  https://chat.zulip.org/#narrow/channel/516-mobile-dev-help/topic/Execution.20failed.20for.20task.20'.3Aapp.3AcompileDebugKotlin'/near/2076887

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

android/gradle.properties

@@ -1,4 +1,4 @@
-org.gradle.jvmargs=-Xmx1536M
+org.gradle.jvmargs=-Xmx3072M
 android.useAndroidX=true
 android.enableJetifier=true