Revert "Add angle_dx11 back to the manifest"

Now that chromium has been brought up to date, we no longer need this old project.
This reverts commit 72a1bb6dac.
Change-Id: I4b25a4729108fe0f925ec98b6bd8e47c625ef581

default.xml

@@ -73,7 +73,6 @@
   <project path="external/chromium_org/testing/gtest" name="platform/external/chromium_org/testing/gtest" />
   <project path="external/chromium_org/third_party/WebKit" name="platform/external/chromium_org/third_party/WebKit" />
   <project path="external/chromium_org/third_party/angle" name="platform/external/chromium_org/third_party/angle" />
-  <project path="external/chromium_org/third_party/angle_dx11" name="platform/external/chromium_org/third_party/angle_dx11" />
   <project path="external/chromium_org/third_party/brotli/src" name="platform/external/chromium_org/third_party/brotli/src" />
   <project path="external/chromium_org/third_party/eyesfree/src/android/java/src/com/googlecode/eyesfree/braille" name="platform/external/chromium_org/third_party/eyesfree/src/android/java/src/com/googlecode/eyesfree/braille" />
   <project path="external/chromium_org/third_party/freetype" name="platform/external/chromium_org/third_party/freetype" />