Fix typos in data_validate.c

[jabuj]

There is a typo in data_validate.c, where time validation doesn't work.

Also changed the spelling of "dropdown" to be consistent across the file.

[mohd-akram]

Also, this:

libxlsxwriter/examples/data_validate.c

Lines 96 to 99 in f2084bc

	data_validation->validate = LXW_VALIDATION_TYPE_INTEGER;
	data_validation->criteria = LXW_VALIDATION_CRITERIA_NOT_BETWEEN;
	data_validation->minimum_formula = "=E3";
	data_validation->maximum_formula = "=F3";

should be changed to LXW_VALIDATION_TYPE_INTEGER_FORMULA

These need to be fixed in docs/src/working_with_data_validation.dox as well.

[jmcnamara]

@jabuj and @mohd-akram thanks for the fixes. I'll make the changes myself since there are a couple of other minor things to be fixed as well.

[jmcnamara]

Fixed on main.