Is `io.sql._SAFE_NAMES_WARNING` still relevant?
#### Is your feature request related to a problem?

When I try to dump a DataFrame which has spaces in columns into an SQLite database, I get the _SAFE_NAMES_WARNING. However, spaces in column names are no longer changed to underscores since version 0.14. This warning should be removed. IMHO it is no longer relevant.

#### Describe the solution you'd like

Remove the following lines from io/sql.py in function `SQLiteTable._create_table_setup`:

```
        pat = re.compile(r"\s+")
        column_names = [col_name for col_name, _, _ in column_names_and_types]
        if any(map(pat.search, column_names)):
            warnings.warn(_SAFE_NAMES_WARNING, stacklevel=6)
```


#### API breaking implications

None

#### Describe alternatives you've considered

None

#### Additional context