Revert "cmake-native.bbclass: Add ubfs specific variable to ignore list"

[kraj]

The problem is in BSP layer [1], these variable should not be exported universally moreover its not needed as well.

[1] https://github.com/varigit/meta-variscite-bsp-imx/pull/36 This reverts commit 288f752445d3783dbaf06a60919a2b35b14e3a62.

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