nvdec: Rely on upstream's value for interlace-mode with hevc

The nvdec API doesn't seem to produce interlacing information with hevc
streams so rely on upstreams value for interlace-mode
6 jobs for nvdec-hevc-interlace in 74 minutes and 38 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #61948
gst indent

00:00:33

passed #61947
manifest

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  Build
passed #61949
build fedora x86_64

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  Test
passed #61950
check fedora

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  Full Builds
passed #61951
build android arm64 api28

00:02:17

passed #61952
build cerbero fedora x86_64

00:55:34