Remove the system-api-stubs-docs target

Nothing consumes the output of this module anymore. The txt files
themselves will be removed in a follow-up change (it is easier after
this build rule stops them changing all the time).

Bug: 171029603
Test: m checkapi with txts removed
Change-Id: Iac487dd6c62504b33cf4e372ba4a7cf9808bf5fc

StubLibraries.bp

@@ -176,31 +176,6 @@ module_libs = " " +
         "client=android.annotation.SystemApi.Client.PRIVILEGED_APPS" +
     "\\) "
 
-droidstubs {
-    name: "system-api-stubs-docs",
-    defaults: ["metalava-full-api-stubs-default"],
-    arg_files: [
-        "core/res/AndroidManifest.xml",
-    ],
-    args: metalava_framework_docs_args + priv_apps,
-    check_api: {
-        current: {
-            api_file: "api/system-current.txt",
-            removed_api_file: "api/system-removed.txt",
-        },
-        last_released: {
-            api_file: ":android.api.system.latest",
-            removed_api_file: ":removed.api.system.latest",
-            baseline_file: ":system-api-incompatibilities-with-last-released"
-        },
-        api_lint: {
-            enabled: true,
-            new_since: ":android.api.system.latest",
-            baseline_file: "api/system-lint-baseline.txt",
-        },
-    },
-}
-
 droidstubs {
     name: "system-api-stubs-docs-non-updatable",
     defaults: ["metalava-non-updatable-api-stubs-default"],