[ci] Android client build does not require secrets
[ci] Android client build does not require secrets

We run builds against external PRs, so that we can merge them with confidence.
We do not expose CI secrets to those builds, so that we can run them with
confidence.  With this change, the android client build will run successfully
for external PRs which do not introduce breaking changes, but produce apps
without our secrets in them.  On master or internal PRs, they will decrypt
secrets as normal.

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