Removing dead ServiceManager constants

Since ServiceManager went away, we're clearing up some leftover
CupsProxyService constants. Trivial change.

Bug: chromium:945409
Test: confirmed service behavior unchanged
Change-Id: I45ffdeb3b0ad1990798a4a4d5115e791a6eefbfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1764430
Auto-Submit: Luum Habtemariam <luum@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689164}

chrome/services/cups_proxy/public/mojom/BUILD.gn

@@ -7,7 +7,6 @@ import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("mojom") {
   sources = [
-    "constants.mojom",
     "proxy.mojom",
   ]
 

chrome/services/cups_proxy/public/mojom/constants.mojom

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-module chromeos.printing.mojom;
-
-// Service id.
-const string kCupsProxyServiceName = "cups_proxy";
-
-// StartCupsProxyService capability id.
-const string kStartCupsProxyServiceCapability = "start_cups_proxy_service";