[Backport 2.x] Update sidecar z-index style #7849

Job	Run time
Run cypress tests (osd:ciGroup1)	13m 53s
Run cypress tests (osd:ciGroup2)	16m 15s
Run cypress tests (osd:ciGroup3)	14m 59s
Run cypress tests (osd:ciGroup4)	13m 41s
Run cypress tests (osd:ciGroup5)	13m 41s
Run cypress tests (osd:ciGroup6)	17m 30s
Run cypress tests (osd:ciGroup7)	16m 44s
Run cypress tests (osd:ciGroup8)	15m 32s
Run cypress tests (osd:ciGroup9)	14m 57s
add-comment	0s
	2h 17m 12s

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