spec/ruby/core/file/utime_spec.rb: far future timestamp may be trancated
spec/ruby/core/file/utime_spec.rb: far future timestamp may be trancated

Under some Ext4 filesystem settings, a timestamp is limited up to
0x37fffffff (2446-05-10).

https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Inode_Timestamps
> Therefore, timestamps should not overflow until May 2446.

Actually the spec fails under one of our CI environments, like:

```
1)
File.utime allows Time instances in the far future to set mtime and atime FAILED
Expected 2446 == 559444
to be truthy but was false
```
https://rubyci.org/logs/rubyci.s3.amazonaws.com/arch/ruby-master/log/20200208T180002Z.fail.html.gz

nobu/rubyspec,ruby/spec,eregon/rubyspec,nobu/rubyspec,nobu/rubyspec,eregon/rubyspec,ruby/spec,eregon/rubyspec,ruby/spec