Update tonic to pull in fixes to assertions and build failures on Windows. (#5833)

DEPS

@@ -126,7 +126,7 @@ deps = {
    Var('fuchsia_git') + '/garnet' + '@' + 'b7492b5f34e32248b164eb48ae8e67995aebda67',
 
   'src/third_party/tonic':
-   Var('fuchsia_git') + '/tonic' + '@' + 'e586d2975fedec0aa6c3ec87de287789172a0948',
+   Var('fuchsia_git') + '/tonic' + '@' + '81fc7ad248fba238a71b04d34595edbe37128346',
 
   'src/third_party/benchmark':
    Var('fuchsia_git') + '/third_party/benchmark' + '@' + '296537bc48d380adf21567c5d736ab79f5363d22',

travis/licenses_golden/licenses_third_party

-Signature: af1324c973cac6d6a9db224502ab1ddf
+Signature: 283abf2ccdd240a0a917afb4e1429f48
 
 UNUSED LICENSES:
 
@@ -21128,7 +21128,6 @@ FILE: ../../../third_party/tonic/file_loader/file_loader_posix.cc
 FILE: ../../../third_party/tonic/file_loader/file_loader_win.cc
 FILE: ../../../third_party/tonic/filesystem/filesystem/path_win.cc
 FILE: ../../../third_party/tonic/filesystem/filesystem/portable_unistd.h
-FILE: ../../../third_party/tonic/filesystem/filesystem/symlink_win.cc
 FILE: ../../../third_party/tonic/platform/platform_utils.h
 FILE: ../../../third_party/tonic/platform/platform_utils_posix.cc
 FILE: ../../../third_party/tonic/platform/platform_utils_win.cc
@@ -21177,20 +21176,11 @@ FILE: ../../../third_party/tonic/dart_sticky_error.cc
 FILE: ../../../third_party/tonic/dart_sticky_error.h
 FILE: ../../../third_party/tonic/file_loader/file_loader.cc
 FILE: ../../../third_party/tonic/file_loader/file_loader.h
-FILE: ../../../third_party/tonic/filesystem/filesystem/build_config.h
-FILE: ../../../third_party/tonic/filesystem/filesystem/directory.cc
-FILE: ../../../third_party/tonic/filesystem/filesystem/directory.h
 FILE: ../../../third_party/tonic/filesystem/filesystem/eintr_wrapper.h
 FILE: ../../../third_party/tonic/filesystem/filesystem/file.cc
 FILE: ../../../third_party/tonic/filesystem/filesystem/file.h
-FILE: ../../../third_party/tonic/filesystem/filesystem/file_descriptor.cc
-FILE: ../../../third_party/tonic/filesystem/filesystem/file_descriptor.h
 FILE: ../../../third_party/tonic/filesystem/filesystem/path.h
 FILE: ../../../third_party/tonic/filesystem/filesystem/path_posix.cc
-FILE: ../../../third_party/tonic/filesystem/filesystem/scoped_temp_dir.cc
-FILE: ../../../third_party/tonic/filesystem/filesystem/scoped_temp_dir.h
-FILE: ../../../third_party/tonic/filesystem/filesystem/symlink.h
-FILE: ../../../third_party/tonic/filesystem/filesystem/symlink_posix.cc
 FILE: ../../../third_party/tonic/logging/dart_error.cc
 FILE: ../../../third_party/tonic/logging/dart_error.h
 FILE: ../../../third_party/tonic/logging/dart_invoke.cc