elif with no expression

## There are elif condition without expression. You can replace  `elif` with `else` to fix. <html>:thumbsup:



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/redis-cpp/detail/config.h:19:6: error: #elif with no expression
![image](https://user-images.githubusercontent.com/77725216/213705984-076105d0-4b6f-4fdd-9452-e1e84d631206.png)