RFR: 8278885: Remove Windows ARM64 int8_t workaround in G1

[Thomas Schatzl]

On Thu, 16 Dec 2021 23:44:55 GMT, aamarsh <duke at openjdk.java.net> wrote:

> Please review this small change to revert a previous workaround that avoided an MSVC issue. 
> 
> This issue has now been fixed in VS 16.8 and higher. 
> 
> I also updated some documentation to reflect this change.

GC changes look good.

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6872