Remove unneeded VirtualPage "__atk_tab" code #30537

Job	Run time
Docs	30s
Smoke (latest, Phpunit)	24s
Unit (7.4, Phpunit)	1m 58s
Smoke (latest, CodingStyle)	53s
Behat (8.1, Chrome)	5m 13s
Unit (7.4, Phpunit Lowest)	2m 4s
Smoke (latest, StaticAnalysis)	37s
Behat (8.1, Chrome Lowest)	5m 18s
Unit (8.0, Phpunit)	1m 58s
Behat (8.2, Chrome)	5m 8s
Unit (8.0, Phpunit Lowest)	2m 4s
Behat (8.2, Chrome Lowest)	5m 19s
Unit (8.1, Phpunit)	2m 11s
Behat (8.3, Chrome)	13m 36s
Unit (8.1, Phpunit Lowest)	2m 3s
Behat (8.3, Chrome Lowest)	5m 32s
Unit (8.2, Phpunit)	1m 57s
Behat (latest, Firefox)	5m 39s
Unit (8.2, Phpunit Lowest)	2m 2s
Behat (latest, Chrome Slow)	9m 56s
Unit (8.3, Phpunit)	3m 43s
Behat (latest, Firefox Slow)	7m 59s
Unit (8.3, Phpunit Lowest)	2m 20s
Unit (latest, Phpunit Burn)	5m 37s
	1h 34m 1s

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