Remove indirection of cpufeatures.gypi.
Now that android_webview_build is no longer supported, the extra level
of indirection of including cpufeatures.gypi instead of directly
depending on the cpufeatures target is not necessary. Remove the cases
in the Chromium tree. Other references appear in projects pulled in via
DEPS that will have to be fixed separately before cpufeatures.gypi can
be entirely deleted.
BUG=440793
Review URL: https://codereview.chromium.org/
1045123005
Cr-Commit-Position: refs/heads/master@{#324117}