[PE] Skip test_sdpa_can_dispatch_on_flash for TimmWrapper-backed models (#48064)

* [PE] Skip test_sdpa_can_dispatch_on_flash for TimmWrapper-backed models

TimmWrapper declares _supports_sdpa=True (timm uses F.scaled_dot_product_attention
internally), but timm does not expose an API to restrict to flash-only dispatch.
The test forces sdpa_kernel(enable_flash=True, enable_math=False, enable_mem_efficient=False),
which causes RuntimeError: No available kernel for PeAudioVideoEncoderTest and
PeVideoEncoderTest. Skip until timm supports controllable attention dispatch.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Remove extra skip from PeVideoModelTest (only EncoderTest reported failing in CI)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Fix indentation error left by previous edit

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>