Revert "Reenable ECKEncryptedMediaTest.MultipleCdmTypes"

This reverts commit 36285ef13dd638a818e41c1640678df4780a4792. But
kept the change in media/test/data/multiple_cdm_types.html.

Reason for revert: Test failure. See crbug.com/348996697.

Original change's description:
> Reenable ECKEncryptedMediaTest.MultipleCdmTypes
>
> Bug: b/40916095
> Change-Id: Ib0ba7fcbf545380ddc213825c911a7bf6966de4e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5571678
> Reviewed-by: John Rummell <jrummell@chromium.org>
> Reviewed-by: Sangbaek Park <sangbaekpark@chromium.org>
> Commit-Queue: Feras Aldahlawi <feras@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1308090}

Bug: b/40916095, 348996697
Change-Id: I335463c15c289808a3c21feae175d502ddbebd13
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5665720
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1321043}