[vm/ffi] Update `DynamicLibrary.process()` documentation
[vm/ffi] Update `DynamicLibrary.process()` documentation

https://dart-review.googlesource.com/c/sdk/+/260760 added support for
Windows to `DynamicLibrary.process()` but forgot to update the dartdoc
comment.

Change-Id: Ic8533e4d1bb23009753bcdef446e2cfe49dea0f6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/264940
Commit-Queue: Daco Harkes <930cbae0ca77f1954c53e32620d89cfcca318f00@google.com>
Auto-Submit: Daco Harkes <930cbae0ca77f1954c53e32620d89cfcca318f00@google.com>
Reviewed-by: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>
Commit-Queue: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk