Android: Update third_party/guava

Upstream guava has switched to full and -android versions. We should
also switch to it due to incompatibilities with dexing. Future versions
of third_party/auto will need full guava 21+ and other third_party
libraries need the android version.

Also added some cipd instructions, these may be outdated soon but are
useful in the meantime.

Bug: None
Change-Id: I7f15368664fbbbd7950feb38d978aa251effa354
Reviewed-on: https://chromium-review.googlesource.com/871870
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#530168}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 4689398543791657407ef2e12446865cb995a633

cipd/android/android.ensure

@@ -70,7 +70,7 @@ chromium/third_party/gson version:2.8.0-cr0
 # endless merge conflicts
 
 @Subdir third_party/guava
-chromium/third_party/guava version:20.0-cr0
+chromium/third_party/guava version:23.0-cr0
 
 # Three unchanging lines
 # avoid the horror that is