[SPIR-V] Update llvm/Maintainers.md

Author: michalpaszkowski

llvm/Maintainers.md

@@ -269,8 +269,11 @@ [email protected] (email), [koachan](https://github.com/koachan) (GitHub)
 
 #### SPIRV backend
 
-Ilia Diachkov \
-[email protected] (email), [iliya-diyachkov](https://github.com/iliya-diyachkov) (GitHub)
+Vyacheslav Levytskyy \
+[email protected], [email protected] (email), [VyacheslavLevytskyy](https://github.com/VyacheslavLevytskyy) (GitHub)
+
+Nathan Gauër \
+[email protected] (email), [Keenuts](https://github.com/Keenuts) (GitHub)
 
 #### SystemZ backend