assistant: remove deprecated deps

Bug: None
Test: locally build
Change-Id: If7f936051ecc056969e10328fed1ffe257cce226
Reviewed-on: https://chromium-review.googlesource.com/c/1297351Reviewed-by: Tao Wu <wutao@chromium.org>
Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602132}

chromeos/services/assistant/BUILD.gn

@@ -75,8 +75,6 @@ source_set("lib") {
       "//chromeos/resources",
       "//chromeos/services/assistant/public/proto",
       "//chromeos/strings",
-      "//libassistant/contrib/core",
-      "//libassistant/contrib/platform/audio",
       "//libassistant/shared/internal_api/c:api_wrappers_entrypoint",
       "//libassistant/shared/public",
       "//libassistant/shared/public:export",
@@ -86,11 +84,6 @@ source_set("lib") {
     ]
 
     libs = [ "$root_out_dir/libassistant.so" ]
-
-    include_dirs = [
-      "//libassistant/contrib",
-      "//libassistant/shared",
-    ]
   }
 }