Since interface-descriptors-ppc.h is removed, so remove it from v8.gyp as well.

R=machenbach@chromium.org,joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1864593002

Cr-Commit-Position: refs/heads/master@{#35276}