docs: Updated code example to prevent syntax error

[ace-builds]

Changes Made

The code example in docs contains a syntax error caused by capitalization

import TimeZone from 'react-native-timezone';

in the above, TimeZone is wrong as other implementations in the docs reference Timezone eg.

const timezone = Timezone.getTimeZone();

change the capitalization of "Z" to lowercase in "TimeZone" fixes the issue