Ignoring AM abbreviation leads to wrong processing the 12th hour.

**Bug reproducing**
```sql
SELECT
    parseDateTimeBestEffort('2020-02-01 12:10:00 AM') AS am,
    parseDateTimeBestEffort('2020-02-01 12:10:00 PM') AS pm

┌──────────────────am─┬──────────────────pm─┐
│ 2020-02-01 12:10:00 │ 2020-02-01 12:10:00 │
└─────────────────────┴─────────────────────┘
```

**Expected behavior**
```sql
┌──────────────────am─┬──────────────────pm─┐
│ 2020-02-01 00:10:00 │ 2020-02-01 12:10:00 │
└─────────────────────┴─────────────────────┘
```
readDecimalNumber<1>(minute, digits);
                    else
                        return on_error("Cannot read DateTime: unexpected number of decimal digits after hour: " + toString(num_digits), ErrorCodes::CANNOT_PARSE_DATETIME);
                    if (checkChar(':', in))
                    {
                        num_digits = readDigits(digits, sizeof(digits), in);
                        if (num_digits == 2)
                            readDecimalNumber<2>(second, digits);
                        else if (num_digits == 1)
                            readDecimalNumber<1>(second, digits);
                        else
                            return on_error("Cannot read DateTime: unexpected number of decimal digits after hour and minute: " + toString(num_digits), ErrorCodes::CANNOT_PARSE_DATETIME);
                    }
                }
                else if (checkChar('/', in) || checkChar('.', in) || checkChar('-', in))
                {
                    if (day_of_month)
                        return on_error("Cannot read DateTime: day of month is duplicated", ErrorCodes::CANNOT_PARSE_DATETIME);
                    if (month)
                        return on_error("Cannot read DateTime: month is duplicated", ErrorCodes::CANNOT_PARSE_DATETIME);
                    if constexpr (is_us_style)
                    {
                        month = hour_or_day_of_month_or_month;
                        num_digits = readDigits(digits, sizeof(digits), in);
                        if (num_digits == 2)
                            readDecimalNumber<2>(day_of_month, digits);
                        else if (num_digits == 1)
                            readDecimalNumber<1>(day_of_month, digits);
                        else
                            return on_error("Cannot read DateTime: unexpected number of decimal digits after month: " + toString(num_digits), ErrorCodes::CANNOT_PARSE_DATETIME);