Add new line to lint's README

Preview of README in
http://cs/android/frameworks/base/tools/lint/README.md?rcl=e5834d57c964cb234a85e27b1e270e46825e7e68
is missing a new line

Bug: 157626959
Test: N/A
Change-Id: I7b80920de8144fe62e6ae0d21718ce4eaee16a20
1 file changed