Remove spaces from DEFAULT_TIDY_HEADER_DIRS

I'm preparing to move this to Soong, and it's simpler to compare if the
spaces are removed here (to match the other lists in this file).

Test: WITH_TIDY=true; compare build.ninja before and after change
Change-Id: Ib27a19a36ebb1132300a8c1eeace1202685dfc4c
1 file changed