Change version to 1.78.0 (#8761)

RELEASE NOTES: N/A

Co-authored-by: Madhav Bissa <[email protected]>

Author: eshitachandwani

version.go

@@ -19,4 +19,4 @@
 package grpc
 
 // Version is the current grpc version.
-const Version = "1.78.0-dev"
+const Version = "1.78.0"