Switch to source-built GSON. am: 55f629c89c am: d1136c4027 am: 9896636be3 am: 54f72d80db am: 506c1a0d17

Original change: https://android-review.googlesource.com/c/platform/prebuilts/manifest-merger/+/2215267

Change-Id: I5b250866169d2a1aec38ef1b70f47563ddc7ac95
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>