[lldb][NFC] Turn ChildCacheState into an unscoped enum (#88703)

Done for consistency with the rest of the enums in
`lldb-enumerations.h`. See
#80167 (comment)

Author: Michael137

lldb/include/lldb/lldb-enumerations.h

@@ -1310,7 +1310,7 @@ enum CompletionType {
 
 /// Specifies if children need to be re-computed
 /// after a call to \ref SyntheticChildrenFrontEnd::Update.
-enum class ChildCacheState {
+enum ChildCacheState {
   eRefetch = 0, ///< Children need to be recomputed dynamically.
 
   eReuse = 1, ///< Children did not change and don't need to be recomputed;