fix: keep default index version unchanged

Author: marcelo-cjl

include/knowhere/version.h

@@ -21,8 +21,8 @@ namespace knowhere {
 namespace {
 static constexpr int32_t default_version = 0;
 static constexpr int32_t minimal_version = 0;
-static constexpr int32_t current_version = 12;
-static constexpr int32_t maximum_version = 12;
+static constexpr int32_t current_version = 8;
+static constexpr int32_t maximum_version = 11;
 }  // namespace
 
 class Version {