Modify assert condition not to be affected by bind variable naming conventions

This pull request updates `test_relation_to_sql` assert_no_match conditions to make this test works as expected. Because of these following reasons:

- Oracle enhanced adapter does not support this feature yet, `to_sql` shows bind variables, which should not. But this test has been passed because of bind value naming convention differences.

- Each database has their own bind parameter naming convention. SQLite and MySQL use `?`, PostgreSQL uses `$` , then Oracle uses `:a1`. In case for future regressions this test has been modified to use literal value.

Here are details.

# oracle
- Actual SQL statement executed at Oracle when `Post.first.comments` executed
```sql
  Comment Load (5.9ms)  SELECT "COMMENTS".* FROM "COMMENTS" WHERE "COMMENTS"."POST_ID" = :a1  [["post_id", 1]]```
```

- `Post.first.comments.to_sql` with oracle enhanced adapter
```ruby
(rdb:1)  Post.first.comments.to_sql
"SELECT \"COMMENTS\".* FROM \"COMMENTS\" WHERE \"COMMENTS\".\"POST_ID\" = :a1"
```

# sqlite3
- Actual SQL statement executed at sqlite3 when `Post.first.comments` executed
```sql
  Comment Load (0.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = ?  [["post_id", 1]]
```
- `Post.first.comments.to_sql` with sqlite3 adapter 
```ruby
(rdb:1) Post.first.comments.to_sql
"SELECT \"comments\".* FROM \"comments\" WHERE \"comments\".\"post_id\" = 1"
```

# mysql
- Actual SQL statement executed
```sql
  Comment Load (0.6ms)  SELECT `comments`.* FROM `comments` WHERE `comments`.`post_id` = ?  [["post_id", 1]]
```
- `Post.first.comments.to_sql` with mysql adapter
```ruby
(rdb:1)  Post.first.comments.to_sql
"SELECT `comments`.* FROM `comments` WHERE `comments`.`post_id` = 1"
```
# mysql2
- Actual SQL statement executed
```sql
  Comment Load (0.4ms)  SELECT `comments`.* FROM `comments` WHERE `comments`.`post_id` = 1
```
- `Post.first.comments.to_sql` with mysql2 adapter 
```ruby
(rdb:1) Post.first.comments.to_sql
"SELECT `comments`.* FROM `comments` WHERE `comments`.`post_id` = 1"
```
# postgresql
- Actual SQL statement executed
```sql
  Comment Load (0.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = $1  [["post_id", 1]]
```
- `Post.first.comments.to_sql` with postgresql adapter 
```ruby
(rdb:1) Post.first.comments.to_sql
"SELECT \"comments\".* FROM \"comments\" WHERE \"comments\".\"post_id\" = 1"
```