Bump min windows version from vista to win8.

Author: evoskuil

builds/msvc/vs2022/libbitcoin-system.import.props

@@ -49,7 +49,7 @@
       <!-- WITH_ICU always defined in Visual Studio builds. -->
       <!-- NOMINMAX enables use of std::min/max without conflict. -->
       <!-- WIN32_LEAN_AND_MEAN avoids inclusion of certain headers, winsock.h conflicts with boost and protocol use of winsock2.h. -->
-      <PreprocessorDefinitions>WITH_ICU;WIN32_LEAN_AND_MEAN;NOMINMAX;_WIN32_WINNT=0x0600;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WITH_ICU;WIN32_LEAN_AND_MEAN;NOMINMAX;_WIN32_WINNT=0x0602;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <!-- Disable auto-linking for all boost-json and its dependency boost-container so they can be header only. -->
       <PreprocessorDefinitions>BOOST_JSON_NO_LIB;BOOST_CONTAINER_NO_LIB;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="'$(Linkage-libbitcoin-system)' == 'static' Or '$(Linkage-libbitcoin-system)' == 'ltcg'">BC_STATIC;%(PreprocessorDefinitions)</PreprocessorDefinitions>