header-checker: Fix unit test include directories

This commit fixes the built-in include directories for header-abi-dumper
unit test cases. Remove the reference to
`prebuilts/sdk/renderscript/clang-include` because we don't check out
`prebuilts/sdk` in `aosp-clang-tools` branch.

Test: PATH=out/soong/dist/bin:$PATH \
development/vndk/tools/header-checker/tests/test.py

Change-Id: Ieb24b0a53b719f4569149251efcdaa3722c0b88c