Revert "Check-in CIPD ninja.exe as a workaround"

This reverts commit c5c48533.

Reason for revert: This breaks infra builders.
https://ci.chromium.org/ui/p/infra/builders/try/infra-try-win/b8811240099559668929/overview
https://ci.chromium.org/ui/p/infra/builders/ci/infra-continuous-win10-64/34002/overview


Original change's description:
> Check-in CIPD ninja.exe as a workaround
>
> There are still some places that directly calls depot_tools/ninja{,.exe} without ensuring .cipd_bin dir.
> This is a binary build on 3pp CIPD pipeline specified in cipd_manifest.txt.
>
> Bug: 931218
> Change-Id: I9f455bf47d648ce8e5bf74bd6c6d356867766314
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3708571
> Auto-Submit: Junji Watanabe <jwata@google.com>
> Reviewed-by: Josip Sokcevic <sokcevic@google.com>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

Bug: 931218
Change-Id: I3f93f029ef6e81f022007cd2ce273d2dd87fd2d4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3708293
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Owners-Override: Takuto Ikuta <tikuta@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Junji Watanabe <jwata@google.com>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>

.gitignore

@@ -7,9 +7,7 @@
 /.versions
 
 # ignore ninja.exe copied from .cipd_bin.
-# TODO(crbug.com/931218): checkin ninja.exe for issues that can't ensure
-# ninja.exe as expected.
-# /ninja.exe
+/ninja.exe
 
 # Ignore "disable auto update" sentinel file.
 .disable_auto_update

cipd_bin_setup.bat

@@ -5,5 +5,4 @@
 
 call "%~dp0\cipd.bat" ensure -log-level warning -ensure-file "%~dp0\cipd_manifest.txt" -root "%~dp0\.cipd_bin"
 :: copy ninja.exe to the root since many places assume ninja.exe exists in depot_tools.
-:: TODO(crbug.com/931218): check in ninja.exe for now.
-:: copy /y "%~dp0\.cipd_bin\ninja.exe" "%~dp0\ninja.exe" > nul
+copy /y "%~dp0\.cipd_bin\ninja.exe" "%~dp0\ninja.exe" > nul