Clarify inconsistent docs on DaggerBroadcastReceiver
Clarify inconsistent docs on DaggerBroadcastReceiver

Fixes https://github.com/google/dagger/issues/1031

RELNOTES=Clarified `DaggerBroadcastReceiver` documentation with respect to when injection is performed

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=182056847

google/dagger,cgruber/dagger,ronshapiro/dagger,google/dagger,ronshapiro/dagger,ze-pequeno/dagger,dushmis/dagger,ze-pequeno/dagger,ze-pequeno/dagger,cgruber/dagger,google/dagger,cgruber/dagger,ze-pequeno/dagger,google/dagger,dushmis/dagger,ronshapiro/dagger