Pre-2006 timing data is incorrect because of change in WNBA clock rules

[BrandanW]

Describe the bug
Before 2006, the WNBA played two 20-minute halves. Beginning in the 2006 season, they switched to 4 10-minute quarters. This impacts many of the assumptions that appear to be driving the timekeeping logic in the end_half_seconds_remaining and end_game_seconds_remaining columns. This also impacts the period_display_value column.

To Reproduce

> pbp_season <- load_wnba_pbp(seasons = 2005)
> table(pbp_season$period_display_value)
1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 
      41715       43840         718         221

> pbp_season <- load_wnba_pbp(seasons = 2006)
> table(pbp_season$period_display_value)
1st Quarter 2nd Quarter         2OT         3OT 3rd Quarter 4th Quarter          OT 
      23529       24676          85          39       24162       26124         468 

This occurs because the first and second half are tagged as "1st Quarter" and "2nd Quarter", OT as "3rd Quarter", and 2OT as "4th Quarter" (and 2005 did not have any games that reached 3OT).

Expected behavior
Before 2006, I expect the end of a game to be the end of the second period, and seconds remaining to be reflecting this clock difference.

Screenshots
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Additional context
Data bug, not usage or functionality.