Remove claims that guava-android works under Java 7.
Remove claims that guava-android works under Java 7.

As of 31.0, it no longer does.

Relevant to https://github.com/google/guava/issues/5269

RELNOTES=n/a
PiperOrigin-RevId: 399330047

mosoft521/guava,mosoft521/guava,google/guava,google/guava,mosoft521/guava,google/guava