Remove libxml from google_apis dependencies.

BUG=604167

Review URL: https://codereview.chromium.org/1893143002

Cr-Commit-Position: refs/heads/master@{#388663}

google_apis/google_apis.gyp

@@ -22,7 +22,6 @@
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../crypto/crypto.gyp:crypto',
         '../net/net.gyp:net',
-        '../third_party/libxml/libxml.gyp:libxml',
         '../url/url.gyp:url_lib',
       ],
       'conditions': [