Remove third_party/aosp (obsolete linker) from DEPS.

This contains an ancient version of gold, which has not been
updated since 2012. Back in times the NDK didn't provide a 64-bit
version of the linker for Android.
This seems to be unused today. It's cleanup time.

BUG=

Review URL: https://codereview.chromium.org/572233003

Cr-Commit-Position: refs/heads/master@{#295096}

.gitignore

@@ -221,7 +221,6 @@ v8.log
 /third_party/android_webview_glue/src
 /third_party/angle
 /third_party/angle_dx11
-/third_party/aosp
 /third_party/apache-mime4j
 /third_party/apache-win32/bin/*.exe
 /third_party/apache-win32/bin/*.dll

DEPS

@@ -468,9 +468,6 @@ deps_os = {
     'src/third_party/android_tools':
      Var('chromium_git') + '/android_tools.git' + '@' + '7fc902d157a9aed7a2b68adc9c69181b3a43cd58',
 
-    'src/third_party/aosp':
-     Var('chromium_git') + '/chromium/deps/aosp.git' + '@' + 'bbafe5155dff86bbba1e92b42a073ffcfcfbf28c',
-
     'src/third_party/apache-mime4j':
      Var('chromium_git') + '/chromium/deps/apache-mime4j.git' + '@' + '28cb1108bff4b6cf0a2e86ff58b3d025934ebe3a',