Remove the dependencies to ext and framework from the stubs build

The two dependencies are not needed. This will cut the circular
dependency that might happen when we separate some framework classes
into a separate jar.

Bug: 135922046
Test: m api-stubs-docs system-api-stubs-docs

Change-Id: I63fc1bce5f2a51366580b5ed3b53c03377a797b2

Android.bp

@@ -1272,10 +1272,6 @@ stubs_defaults {
     srcs_lib: "framework",
     srcs_lib_whitelist_dirs: frameworks_base_subdirs,
     srcs_lib_whitelist_pkgs: packages_to_document,
-    libs: [
-        "ext",
-        "framework",
-    ],
     local_sourcepaths: frameworks_base_subdirs,
     installable: false,
     annotations_enabled: true,