[parser] Move context tests into a separate file

v3/internal/parser/testdata/function_single/main.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"context"
 	_ "embed"
 	"log"
 
@@ -19,11 +18,6 @@ func (*GreetService) Greet(name string) string {
 	return "Hello " + name
 }
 
-// Greet someone
-func (*GreetService) GreetWithContext(ctx context.Context, name string) string {
-	return "Hello " + name
-}
-
 func NewGreetService() *GreetService {
 	return &GreetService{}
 }