web_tests: Remove invalid native-file-system expectations.

This CL removes expectations for non-existing tests. The first two tests
were renamed a while ago. The last test no longer has .tentative. in
its name.

Change-Id: Ib89bfff349800d76a8ab4287beefc14d53e20b45
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2285043Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Auto-Submit: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786004}

third_party/blink/web_tests/FlagExpectations/disable-layout-ng

@@ -557,9 +557,6 @@ virtual/forced-high-contrast-colors/fast/css/forced-colors-mode/backplate/forced
 
 # 10/27/2019 updates.
 external/wpt/css/css-writing-modes/wm-propagation-body-044.html [ Failure ]
-external/wpt/native-file-system/sandboxed_FileSystemBaseHandle-postMessage-MessagePort.tentative.https.window.html [ Crash ]
-external/wpt/native-file-system/sandboxed_FileSystemBaseHandle-postMessage.tentative.https.window.html [ Crash ]
-external/wpt/native-file-system/sandboxed_FileSystemDirectoryHandle-getFile.tentative.https.any.html [ Crash ]
 
 crbug.com/591099 paint/invalidation/compositing/composited-float-under-composited-inline-individual.html [ Failure ]
 crbug.com/591099 paint/invalidation/compositing/composited-float-under-composited-inline.html [ Failure ]