PPC: Remove unnecessay file from v8.gyp

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}

tools/gyp/v8.gyp

@@ -1552,7 +1552,6 @@
             '../../src/ppc/frames-ppc.cc',
             '../../src/ppc/frames-ppc.h',
             '../../src/ppc/interface-descriptors-ppc.cc',
-            '../../src/ppc/interface-descriptors-ppc.h',
             '../../src/ppc/macro-assembler-ppc.cc',
             '../../src/ppc/macro-assembler-ppc.h',
             '../../src/ppc/simulator-ppc.cc',