[Docs] Correct date rounding example for range query

[cbuescher]

Looking into #50237 I realized that two of the examples given in the
documentation around date math rounding for range queries on date fields using
gt and lt is slightly off by a nanosecond. This PR changes this to the
bounds that are currently parsed using these parameters.

[elasticmachine]

Pinging @elastic/es-search (:Search/Search)

[elasticmachine]

Pinging @elastic/es-docs (>docs)

[cbuescher]

Code used to check the differing gt and lt bounds, e.g. run this in RangeFieldTypeTests:

public void testCheckBoundsOnDateFieldType() {
        String dateString = "2014-11-18||/M";
        boolean includeLower = false;
        boolean includeUpper = false;
        DateFieldType dateFieldType = new DateFieldType();

        final DateFormatter formatter = DateFormatter.forPattern("yyyy-MM-dd");
        dateFieldType.setName("field");
        dateFieldType.setDateTimeFormatter(formatter);

        QueryShardContext context = createContext();
        Query query = dateFieldType.rangeQuery(dateString, null, includeLower, includeUpper, ShapeRelation.INTERSECTS, null, null, context);
        assertEquals("field:[1417392000000 TO 9223372036854775807]", query.toString());
        final DateFormatter fullFormatter = DateFormatter.forPattern("strictDateTime");
        assertEquals("2014-12-01T00:00:00.000Z", fullFormatter.formatMillis(1417392000000l));

        query = dateFieldType.rangeQuery(null, dateString, includeLower, includeUpper, ShapeRelation.INTERSECTS, null, null, context);
        assertEquals("field:[-9223372036854775808 TO 1414799999999]", query.toString());
        assertEquals("2014-10-31T23:59:59.999Z", fullFormatter.formatMillis(1414799999999l));
    }

[cbuescher]

@jpountz I just found this looking through my open PRs and updated it with a small correction regarding the rounding resolution, I think the change still applies and I'd like to get it into the current docs. Would you mind taking a look or let me know if I should ask for another review if you don't find the time?