Bump the podspec iOS min to 9.0
Bump the podspec iOS min to 9.0

Xcode 12+ issue a warning when targeting older iOS versions, so avoid
the issue. #7980 updated the Xcode projects already.

google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf