Make test case consistent with comments

Original test case had failed with Tarantool 2.8.1 or newer due to error
message rework [1]. Based on code comments and @funny-falcon response
in #105, the test has been planned to be success insert test and not
a duplicate key error test. This patch changes test case and asserts
to its original idea. Since duplicate key test already exists
in tarantool_test.go file [2], coverage should not decrease.

1. tarantool/tarantool@d11fb30
2. https://github.com/tarantool/go-tarantool/blob/61f3a41907b6bcb060e9fa07069cde5b33ba9764/tarantool_test.go#L437-L443

Closes #105

Author: DifferentialOrange

example_test.go

@@ -119,7 +119,7 @@ func Example() {
 	fmt.Println("Insert Data", resp.Data)
 
 	// insert new tuple { 11, 1 }
-	resp, err = client.Insert("test", &Tuple{Id: 10, Msg: "test", Name: "one"})
+	resp, err = client.Insert("test", &Tuple{Id: 11, Msg: "test", Name: "one"})
 	fmt.Println("Insert Error", err)
 	fmt.Println("Insert Code", resp.Code)
 	fmt.Println("Insert Data", resp.Data)
@@ -194,9 +194,9 @@ func Example() {
 	// Insert Error <nil>
 	// Insert Code 0
 	// Insert Data [[10 test one]]
-	// Insert Error Duplicate key exists in unique index 'primary' in space 'test' (0x3)
-	// Insert Code 3
-	// Insert Data []
+	// Insert Error <nil>
+	// Insert Code 0
+	// Insert Data [[11 test one]]
 	// Delete Error <nil>
 	// Delete Code 0
 	// Delete Data [[10 test one]]