Bump version to 7.6.4

Author: xuzhg

tools/WebStack.versions.settings.targets

@@ -5,7 +5,7 @@
   <PropertyGroup>
     <VersionMajor Condition="'$(VersionMajor)' == ''">7</VersionMajor>
     <VersionMinor Condition="'$(VersionMinor)' == ''">6</VersionMinor>
-    <VersionBuild Condition="'$(VersionBuild)' == ''">3</VersionBuild>
+    <VersionBuild Condition="'$(VersionBuild)' == ''">4</VersionBuild>
     <VersionRelease Condition="'$(VersionRelease)' == ''"></VersionRelease>
   </PropertyGroup>