fix: OS/2 table version is bumped from 5 to 4

[yisibl]

OS/2 Version 5 is not supported in the Android 5 browser.

Fixes:

• https://github.com/thx/iconfont-plus/issues/1999
• https://github.com/thx/iconfont-plus/issues/2001
• https://github.com/thx/iconfont-plus/issues/2003

Before

Test case: https://at.alicdn.com/t/project/689429/4bdadfcb-9406-4c89-927b-421a1179862a.html

After

Test case: https://at.alicdn.com/t/project/689429/61d9cd01-ca82-439d-bbec-0aca73d3b180.html

[puzrin]

Thanks! Can i release or more changes (PR) expected?

[yisibl]

You're welcome, of course.