Preprocess privacy_page_browser_proxy for os_settings rollup

This file has <if> statements which were included
in os_settings_rollup.js because the preprocess="true"
argument was omitted.

Bug: 1045266
Change-Id: Iaaa99a177806d044a87a3af8a87877ab8fe5c39f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2372728
Commit-Queue: Claude van der Merwe <cvandermerwe@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801096}

chrome/browser/resources/settings/chromeos/os_settings_resources_v3.grdp

@@ -194,6 +194,7 @@
   <include name="IDR_OS_SETTINGS_PRIVACY_PAGE_BROWSER_PROXY_M_JS"
            file="${root_gen_dir}/chrome/browser/resources/settings/privacy_page/privacy_page_browser_proxy.m.js"
            use_base_dir="false"
+           preprocess="true"
            compress="false"
            type="BINDATA" />
   <include name="IDR_OS_SETTINGS_PARENTAL_CONTROLS_PAGE_M_JS"