Delete unused .manifest file

chrome.exe.manifest is unreferenced so this change deletes it.

The manifest was added in this change in 2013:
  https://chromiumcodereview.appspot.com/19275010

Over time its functionality was split into separate manifest files and
at some point it stopped being used, perhaps around the change to gn.
Deleting it just finishes the transition.

The separate manifest files which supply the common controls and
requested execution levels which this (unused) file still contains are
referenced from chrome_exe_manifest in
chrome/app/version_assembly/BUILD.gn

Change-Id: I263f4e7aca97c231c846cf264886d3745b22cb7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2163751
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#763388}

chrome/app/chrome.exe.manifest

-<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
-
-  <!--The compatibility section will be merged from build/win/compatibility.manifest -->
-
-  <dependency>
-    <dependentAssembly>
-      <assemblyIdentity type="Win32" name="Microsoft.Windows.Common-Controls" version="6.0.0.0" processorArchitecture="*" publicKeyToken="6595b64144ccf1df" language="*"></assemblyIdentity>
-    </dependentAssembly>
-  </dependency>
-
-  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
-    <security>
-      <requestedPrivileges>
-        <requestedExecutionLevel level="asInvoker" />
-      </requestedPrivileges>
-    </security>
-  </trustInfo>
-
-</assembly>