Remove internal props from api txt files

Internal props are not tracked, so they don't need to be stored in the
api txt file.

Bug: 170693240
Test: sysprop_test && manual test on existing sysprop_library
Change-Id: I32d6ee3235a699f5160644b9e1b43d9cf0da61fc
Merged-In: I32d6ee3235a699f5160644b9e1b43d9cf0da61fc
(cherry picked from commit 656ac0fd59c862e1e10712fbbbc05224fea1b400)
2 files changed