dumpsys: Fix compatibility with newer flatbuffers

GenerateText was renamed to GenText in 23.5.26 because the return
behavior was changed, so support both cases for now.
https://github.com/google/flatbuffers/commit/950a71ab893e96147c30dd91735af6db73f72ae0

Bug: 303433787
Test: m . # and FEATURES=test emerge-${BOARD} chromeos-base/floss

Change-Id: I854fd5196f9a62dd587fec59b9e00d7936c4262d