[LLVM] Update Sparc maintainer (llvm#120430)

Currently vegovin is listed as the maintainer of the Sparc backend,
however they haven't been involved with LLVM for about 10 years already.

Nominate koachan as the new Sparc maintainer.

Author: nikic

llvm/Maintainers.md

@@ -251,8 +251,8 @@ [email protected] (email), [asb](https://github.com/asb) (GitHub)
 
 #### Sparc backend
 
-Venkatraman Govindaraju \
-[email protected] (email), [vegovin](https://github.com/vegovin) (GitHub)
+Koakuma \
+[email protected] (email), [koachan](https://github.com/koachan) (GitHub)
 
 #### SPIRV backend
 
@@ -459,6 +459,7 @@ Chandler Carruth ([email protected], [email protected], [chandlerc](https:/
 Evan Cheng ([email protected]) -- Parts of code generator not covered by someone else \
 Jake Ehrlich ([email protected], [jakehehrlich](https://github.com/jakehehrlich)) -- llvm-objcopy and ObjCopy library \
 Renato Golin ([email protected], [rengolin](https://github.com/rengolin)) -- ARM backend \
+Venkatraman Govindaraju ([email protected], [vegovin](https://github.com/vegovin) -- Sparc backend \
 James Grosbach ([email protected]) -- MC layer \
 Anton Korobeynikov ([email protected], [asl](https://github.com/asl)) -- ARM EABI \
 Chad Rosier ([email protected]) -- FastISel \