Suppress flaky update-deps failures for any win32 files

win32/win32.o was also unstable:
https://github.com/ruby/ruby/actions/runs/5628655900/job/15252762821?pr=8107

At this point, any win32 files seem suspicious. Let's just ignore all
such files.

tool/update-deps

@@ -168,10 +168,8 @@ FILES_SAME_NAME_TOP = %w[
 ]
 
 # Files that may or may not exist on CI for some reason.
-# They are probably missing dependencies.
-UNSTABLE_FILES = %w[
-  win32/file.o
-]
+# Windows build generally seems to have missing dependencies.
+UNSTABLE_FILES = %r{\Awin32/[^/]+\.o\z}
 
 # Other source files exist in the source directory.
 
@@ -236,7 +234,9 @@ def in_makefile(target, source)
     else source2 = "$(top_srcdir)/#{source}"
     end
     ["#{File.dirname(target)}/depend", target2, source2]
-  when *UNSTABLE_FILES
+  # Files that may or may not exist on CI for some reason.
+  # Windows build generally seems to have missing dependencies.
+  when UNSTABLE_FILES
     warn "warning: ignoring: #{target}"
   else
     raise "unexpected target: #{target}"