google_apis: Remove Lacros leftovers

Lacros is gone.

- Replace IS_CHROMEOS_ASH uses with IS_CHROMEOS.
- Remove IS_CHROMEOS_LACROS uses.
- Remove includes of build/chromeos_buildflags.h or replace the with
  build/build_config.h.
- Remove imports of chromeos/ui_mode.gni.

Bug: b:354842935
Change-Id: I1c49e9eef253057fc68286fdd1d55d1cf116a486
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6228659
Reviewed-by: Monica Basta <msalama@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1415926}

google_apis/google_api_keys.h

@@ -10,7 +10,6 @@
 #include "base/component_export.h"
 #include "base/functional/callback_helpers.h"
 #include "build/build_config.h"
-#include "build/chromeos_buildflags.h"
 #include "google_apis/buildflags.h"
 
 namespace version_info {
@@ -102,7 +101,7 @@ COMPONENT_EXPORT(GOOGLE_APIS) const std::string& GetSodaAPIKey();
 COMPONENT_EXPORT(GOOGLE_APIS) const std::string& GetHatsAPIKey();
 #endif
 
-#if BUILDFLAG(IS_CHROMEOS_ASH)
+#if BUILDFLAG(IS_CHROMEOS)
 // Retrieves the Sharing API Key.
 COMPONENT_EXPORT(GOOGLE_APIS) const std::string& GetSharingAPIKey();