WPT

fix: do no duplicate headers #12627

Job	Run time
4/6 cd-headless	4m 30s
3/6 cd-headless	5m 17s
5/6 cd-headless	3m 20s
6/6 cd-headful	4m 32s
1/6 cd-headful	5m 14s
1/6 cd-headless	5m 6s
6/6 cd-headless	4m 25s
6/6 node-headless	6m 34s
3/6 cd-headful	4m 55s
4/6 cd-headful	4m 34s
2/6 cd-headless	4m 16s
1/6 node-headless	7m 0s
5/6 node-headless	4m 46s
4/6 node-headless	5m 43s
2/6 node-headless	7m 3s
5/6 cd-headful	3m 37s
2/6 cd-headful	4m 51s
3/6 node-headless	7m 48s
[Required] WPT sink	3s
WPT report	0s
Update WPT expectations (if required)	-1s
Commit updated expectations	-1s
	1h 33m 32s

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