Returns the most recent WNBA Stats API season year as an integer. This
is a thin wrapper around most_recent_wnba_season() kept as a separate
helper for naming symmetry with the wnba_stats_* family of loaders
(mirrors the most_recent_*_season() convention used elsewhere in the
package). The WNBA Stats API and ESPN's WNBA endpoints share the same
calendar-year season identifier, so the returned value is identical
to most_recent_wnba_season().