docs: Rename 'All scenario OS' to 'All scenarios OS'

* All topics revised to reflect All scenarios OS instead of All scenario
  OS to maintain consistency, fixes issue#70

Signed-off-by: Arul Kumaran <arulkumaran.devarajan@huawei.com>
14 jobs for !85 with scenarios in 34 minutes and 41 seconds (queued for 2 seconds)
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  Compliance
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dco

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  Build
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build-docs

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freertos-armv5

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linux-qemu-arm

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linux-qemu-arm64

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linux-qemu-x86

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linux-qemu-x86_64

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linux-seco-imx8mm-c61

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linux-seco-intel-b68

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linux-stm32mp1-av96

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zephyr-96b-avenger

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zephyr-96b-nitrogen

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zephyr-qemu-cortex-m3

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zephyr-qemu-x86

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