Trac 57998: Fix partial hour in current_time()

[hellofromtonya]

Fixes partial-hour timezone calculation in current_time() when 'timestamp' is passed. The gmt_offset can be a float/double for partial-hour timezones such as +5:30 UTC for India and Sri Lanka.

How?

• Changing the int type cast to float for option value.
• Then restoring the int type cast of that calculation, i.e. restoring it before changeset 55054.

Trac ticket: https://core.trac.wordpress.org/ticket/57035

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